ST. LOUIS (AP) — As many as 350 dogs have been seized and about 30 people arrested in raids across five states that animal welfare groups are calling the largest simultaneous raid of dogfighting operations in the U.S.

Authorities said Wednesday that the raids were conducted by federal, state and local law enforcement agencies across Missouri, Illinois, Iowa, Texas and Oklahoma.

The raids followed a more than year-long investigation prompted by information from the Humane Society of Missouri, which says it reached out to others when it realized the scope of the operations.

Dogfighting is a felony throughout the United States.

President George W. Bush signed a law two years ago that increased penalties for activities that promote or encourage animal fighting.