WASHINGTON - 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.

John M. Bales, the U.S. attorney in eastern Texas, said nine people in his state were indicted on June 30 of three counts — conspiracy to commit an offense against the United States, sponsoring or exhibiting an animal in an animal fighting venture and buying, selling, delivering or transporting animals for participation in an animal fighting venture. If convicted, the defendants each face up to five years in federal prison and fines of up to $250,000.

Bales said eight people were arrested Wednesday in Texas' Panola and Gregg counties. Nine dogs, mostly pit bull terriers, were seized during a search of property in rural Panola County.

Bales said a veterinarian and representatives of the Humane Society were caring for the dogs. Bales said he filed motions to put the dogs in the care of the Humane Society and asked a judge to order those charged in the case to reimburse the organization for the cost