LANSING, Mich. -

Michigan's attorney general will investigate possible fraud in a petition debacle that has forced U.S. Rep. Thaddeus McCotter to run for his Detroit-area congressional seat as a write-in candidate.

Republican Attorney General Bill Schuette said Thursday that his office's criminal division will investigate the nominating petitions after getting a referral from the state elections bureau.

"We will follow the facts, without fear or favor,” Schuette said. “It’s our duty to maintain the integrity of our election process.”

McCotter said in a release that he'll cooperate with the investigation.

"I thank the Michigan Secretary of State and Attorney General for commencing the criminal investigation of petitions I requested Tuesday; will assist as they see fit," he said.

The bureau told the congressman last week that it appeared so many of the 2,000 signatures his campaign submitted had problems that he wouldn't have the 1,000 needed to get on the Aug. 7 GOP primary ballot. It said fewer than 250 signatures appeared valid.

The lone Republican candidate now on the 11th District primary ballot is Kerry Bentivolio of Milford.