CNN

PMG Group lobbying activities are under investigation by federal authorities.

WASHINGTON (CNN) - Rep. Pete Visclosky, D-Indiana, confirmed Friday that federal law enforcement officials had issued subpoenas for materials from his congressional and campaign offices in their investigation of a defense lobbying firm that had employed his former chief of staff.

The PMA Group was raided by the FBI earlier this year. Former Visclosky chief of staff Rich Kaelin had lobbied for the firm.

"Federal law enforcement officials have issued grand jury subpoenas to my Congressional office, campaign committees, and certain employees to request documents relating to PMA," Visclosky said in a statement. "It is my intention to fully cooperate with the investigation consistent with my constitutional obligations to Congress and my duties and responsibilities to my constituents.

"I will continue to work hard to represent the people of Indiana's First Congressional District as I have done since being elected to Congress. I am confident that at the end of this process, no one will conclude that I have done anything wrong or harmed my constituents in any way," he said. Citing respect for the investigative process, the congressman said he would not be commenting further on the situation.

Visclosky has returned thousands of dollars in campaign contributions from the firm and its employees, who were among his biggest financial supporters.