HARRISBURG — An FBI official said agents executed search warrants at the home and district office of a top Pennsylvania state senator.

FBI spokesman Frank Burton Jr. said today the agents are investigating allegations of illegal activity by Senate Minority Leader Bob Mellow.

Burton said the investigation is a joint operation between the IRS and the FBI.

He said the agents arrived in the morning at the Democrat's Scranton-area home and office. Burton would not say what they were seeking or discuss the allegations.

Mellow's spokeswoman said he is cooperating and is confident he has done nothing wrong.

Mellow is the state Senate's longest-serving member and is retiring at the end of this year.