diff --git a/src/main/java/crawlercommons/mimetypes/MimeTypeDetector.java b/src/main/java/crawlercommons/mimetypes/MimeTypeDetector.java
index bd61382..74119a1 100644
--- a/src/main/java/crawlercommons/mimetypes/MimeTypeDetector.java
+++ b/src/main/java/crawlercommons/mimetypes/MimeTypeDetector.java
@@ -44,25 +44,33 @@ public class MimeTypeDetector {
                     (byte) 0xBF
                     };
 
+    private static final int LEADING_WHITESPACE_MAX_SKIP = 16;
+
+    private final static boolean[] spaceCharacters = new boolean[256];
+    static {
+        spaceCharacters[0x09] = true; // \t - character tabulation (ht)
+        spaceCharacters[0x0a] = true; // \n - line feed (lf)
+        spaceCharacters[0x0b] = true; // line tabulation (vt)
+        spaceCharacters[0x0c] = true; // form feed (ff)
+        spaceCharacters[0x0d] = true; // \r - carriage return (cr)
+        spaceCharacters[0x20] = true; // space
+    }
+
     private static class MimeTypeEntry {
         private String mimeType;
         private byte[] pattern;
+        private boolean allowBOM;
+        private boolean allowLeadingSpace;
 
         public MimeTypeEntry(String mimeType, String pattern) {
-            this(mimeType, pattern, false);
+            this(mimeType, pattern, false, false);
         }
 
-        public MimeTypeEntry(String mimeType, String pattern, boolean addBOM) {
+        public MimeTypeEntry(String mimeType, String pattern, boolean allowBOM, boolean allowLeadingSpace) {
             this.mimeType = mimeType;
-
-            byte[] patternBytes = pattern.getBytes(StandardCharsets.UTF_8);
-            if (addBOM) {
-                this.pattern = new byte[UTF8_BOM.length + patternBytes.length];
-                System.arraycopy(UTF8_BOM, 0, this.pattern, 0, UTF8_BOM.length);
-                System.arraycopy(patternBytes, 0, this.pattern, UTF8_BOM.length, patternBytes.length);
-            } else {
-                this.pattern = patternBytes;
-            }
+            this.allowBOM = allowBOM;
+            this.allowLeadingSpace = allowLeadingSpace;
+            this.pattern = pattern.getBytes(StandardCharsets.UTF_8);
         }
 
         public MimeTypeEntry(String mimeType, int... pattern) {
@@ -95,43 +103,64 @@ public class MimeTypeDetector {
         mimeTypes = new ArrayList<>();
 
         // Add all text patterns without and with a BOM.
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?xml"));
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?xml", true));
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?XML"));
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?XML", true));
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<!--"));
-        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<!--", true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?xml", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<?XML", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<!--", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<urlset", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<sitemapindex", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<rss", true, true));
+        mimeTypes.add(new MimeTypeEntry(XML_MIMETYPES[0], "<feed", true, true));
 
-        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "http://"));
-        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "http://", true));
-        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "https://"));
-        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "https://", true));
+        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "http://", true, true));
+        mimeTypes.add(new MimeTypeEntry(TEXT_MIMETYPES[0], "https://", true, true));
 
         mimeTypes.add(new MimeTypeEntry(GZIP_MIMETYPES[0], "\037\213"));
         mimeTypes.add(new MimeTypeEntry(GZIP_MIMETYPES[0], 0x1F, 0x8B));
 
         maxPatternLength = 0;
         for (MimeTypeEntry entry : mimeTypes) {
-            maxPatternLength = Math.max(maxPatternLength, entry.getPattern().length);
+            int length = entry.getPattern().length;
+            if (entry.allowBOM)
+                length += UTF8_BOM.length;
+            if (entry.allowLeadingSpace)
+                length += LEADING_WHITESPACE_MAX_SKIP;
+            maxPatternLength = Math.max(maxPatternLength, length);
         }
     }
 
     public String detect(byte[] content) {
-        for (MimeTypeEntry entry : mimeTypes) {
-            if (patternMatches(entry.getPattern(), content, 0, content.length)) {
-                return entry.getMimeType();
-            }
-        }
-
-        // No mime-type detected.
-        return null;
+        return detect(content, 0, content.length);
     }
 
     public String detect(byte[] content, int offset, int length) {
+        int offsetBOM = -1;
+        int offsetSpace = -1;
         for (MimeTypeEntry entry : mimeTypes) {
             if (patternMatches(entry.getPattern(), content, offset, length)) {
                 return entry.getMimeType();
             }
+            if (entry.allowBOM) {
+                if (offsetBOM == -1) {
+                    offsetBOM = offset;
+                    while (patternMatches(UTF8_BOM, content, offsetBOM, length) && offsetBOM < content.length) {
+                        offsetBOM += UTF8_BOM.length;
+                    }
+                }
+                if (patternMatches(entry.getPattern(), content, offsetBOM, length)) {
+                    return entry.getMimeType();
+                }
+            }
+            if (entry.allowLeadingSpace) {
+                if (offsetSpace == -1) {
+                    offsetSpace = (offsetBOM > 0 ? offsetBOM : 0);
+                    while (offsetSpace < content.length && spaceCharacters[content[offsetSpace] & 0xFF]) {
+                        offsetSpace++;
+                    }
+                }
+                if (patternMatches(entry.getPattern(), content, offsetSpace, length)) {
+                    return entry.getMimeType();
+                }
+            }
         }
 
         // No mime-type detected.
@@ -143,7 +172,7 @@ public class MimeTypeDetector {
             return false;
         }
 
-        for (int i = 0; i < pattern.length; i++) {
+        for (int i = 0; i < pattern.length && (offset + i) < content.length; i++) {
             if (pattern[i] != content[offset + i]) {
                 return false;
             }
diff --git a/src/main/java/crawlercommons/sitemaps/SiteMapParser.java b/src/main/java/crawlercommons/sitemaps/SiteMapParser.java
index 3720eb2..b87884d 100644
--- a/src/main/java/crawlercommons/sitemaps/SiteMapParser.java
+++ b/src/main/java/crawlercommons/sitemaps/SiteMapParser.java
@@ -192,6 +192,10 @@ public class SiteMapParser {
         }
 
         String contentType = mimeTypeDetector.detect(content);
+        if (contentType == null) {
+            String msg = String.format(Locale.ROOT, "Failed to detect MediaType of sitemap '%s'", url);
+            throw new UnknownFormatException(msg);
+        }
         return parseSiteMap(contentType, content, url);
     }
 
diff --git a/src/test/java/crawlercommons/mimetypes/MimeTypeDetectorTest.java b/src/test/java/crawlercommons/mimetypes/MimeTypeDetectorTest.java
index bcfa999..7716bb7 100644
--- a/src/test/java/crawlercommons/mimetypes/MimeTypeDetectorTest.java
+++ b/src/test/java/crawlercommons/mimetypes/MimeTypeDetectorTest.java
@@ -53,6 +53,33 @@ public class MimeTypeDetectorTest {
         assertTrue(detector.isGzip(mimeType));
     }
 
+    @Test
+    public void testLeadingSpace() throws IOException {
+        MimeTypeDetector detector = new MimeTypeDetector();
+
+        byte[] whitespace = { (byte) 0x20, (byte) 0x0a };
+        byte[] content = getSitemap("sitemap.txt");
+        byte[] wscontent = new byte[whitespace.length + content.length];
+        System.arraycopy(whitespace, 0, wscontent, 0, whitespace.length);
+        System.arraycopy(content, 0, wscontent, whitespace.length, content.length);
+
+        String mimeType = detector.detect(wscontent);
+        assertFalse(detector.isXml(mimeType));
+        assertTrue(detector.isText(mimeType));
+        assertFalse(detector.isGzip(mimeType));
+
+        content = getSitemap("sitemap-with-bom.txt");
+        wscontent = new byte[whitespace.length + content.length];
+        System.arraycopy(content, 0, wscontent, 0, 3);
+        System.arraycopy(whitespace, 0, wscontent, 3, whitespace.length);
+        System.arraycopy(content, 3, wscontent, (3 + whitespace.length), (content.length - 3));
+
+        mimeType = detector.detect(wscontent);
+        assertFalse(detector.isXml(mimeType));
+        assertTrue(detector.isText(mimeType));
+        assertFalse(detector.isGzip(mimeType));
+    }
+
     private byte[] getSitemap(String filename) throws IOException {
         return IOUtils.toByteArray(MimeTypeDetectorTest.class.getResourceAsStream("/sitemaps/" + filename));
     }