HOUSTON -- Crime Stoppers offered rewards Tuesday to help find 40 people believed to be involved in one of the largest dogfighting operations in the United States, KPRC Local 2 reported. Fifteen pictures of suspects were released.

Harris County District Attorney Kenneth Magidson said more than 100 dogs were seized last week during the investigation that included Harris, Montgomery and Tyler counties.

"They were bred specifically to fight," said Belinda Smith of the Harris County District Attorney's Office. "They are not pets."

Crime Stoppers will pay up to $5,000 for information called in to the 713-222-8477 tips hot line that leads to the capture of any felony suspect charged with dog fighting.

Tips may also be submitted online at www.crime-stoppers.org. All tipsters remain anonymous.

The Texas Department of Public Safety's Criminal Intelligence Service headed up the yearlong investigation.

Investigators said fights were staged in Harris County weekly or twice monthly at one of eight secluded sites. Fifteen to 100 people attended each fight and many wagered on the outcomes, officials said.

Forty-one felony charges were filed, mostly for engaging in dogfighting. A conviction on that charge carries a punishment of up to two years in state jail.

Forty-five other charges were filed for the class A misdemeanor of being a spectator at a dogfight, which is punishable by up to one year in county jail and a $4,000 fine.