The FBI searched the offices of a California state senator and the Legislature's Latino caucus on Tuesday but would not disclose the reason for the investigation.

Laura Eimiller, a spokeswoman for the FBI office in Los Angeles, said the warrants were served at about 3 p.m. and agents remained inside the state Capitol in the evening.

She would not disclose the target of the search warrants, but Senate Chief Sergeant-at-Arms Tony Beard told The Associated Press it was Sen. Ron Calderon, a Democrat from the Los Angeles County city of Montebello.

"It's a federal search warrant served on Sen. Calderon's office. It's a sealed search warrant. I don't know what it relates to," Beard said.

He said Calderon was not present during the search and he did not know if the agents had removed any material.

Calderon did not immediately return a message left on his cellphone. His spokesman, Rocky Rushing, said he could not comment and referred calls to Los Angeles attorney Mark Geragos. Geragos did not immediately return messages left on his office and cellular phones.

Beard also told reporters who gathered outside Calderon's office Tuesday night that the office of the Latino Legislative Caucus, which is across the street from the Capitol in the Legislative Office Building, also was searched. A spokeswoman for the caucus, Lizette Mata, did not immediately return telephone and email messages.

Eimiller said the investigation is being led by federal authorities in Southern California, where Calderon is based. Two warrants had been issued and were under seal in U.S. District Court, but she did not know if that was in Los Angeles or Sacramento.

Calderon is part of a powerful Southern California political dynasty. His two brothers served in the state Legislature and his nephew, Ian Calderon, was elected to the Assembly last year.

Calderon is known as a moderate, business-friendly Democrat. After his election to the Assembly in 2002, he was a member of the Assembly Moderate Caucus.