The Humane Society of the United States (HSUS) has a national hotline (877-TIP-HSUS) and offers $5000 for tips leading to arrest and conviction of dogfighting or cockfighting participants. You can also order an Action Pack via email to help spread the word, and check out their Taking Action page for more information on how to help.
Pit Bull Rescue Central offers a list of links to organizations who offer rewards for tips leading to the arrest and convictions of blood sport participants on their Rewards page.
The ASPCA offers a wealth of information regarding dog fighting including the history of the "sport" and how you can help put a stop to it.
If you know of a dogfight in progress contact your local police department and follow up with the HSUS, the local media, and anyone else who can help the situation. This is not a game or a sport. It is animal cruelty, and its human participants are criminals who are often associated with gangs, drugs, illegal weapons, and much more along with the dog fighting.
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