WASHINGTON (AP) – A federal grand jury has subpoenaed a Democratic congressman in a corruption probe, the first concrete indication that a long-simmering Justice Department investigation of a top lobbying firm also has the potential to seriously damage congressional careers.

On Friday, Rep. Pete Visclosky, R-Ind., acknowledged the grand jury has demanded documents from his office, some employees and his campaign committees.

The probe focuses on the PMA Group, a now-defunct lobbying firm that specialized in securing federal contracts for defense firms from Visclosky, Rep. John Murtha, D-Pa., and others on the House Appropriations defense subcommittee that Murtha chairs.

In his hometown of Johnstown, Pa., Murtha brushed aside questions Friday about one Pennsylvania defense contractor for whom he obtained $14.7 million in the last two years in congressionally directed funds called “earmarks.” The Navy suspended the contractor a month ago for alleged fraud.

Murtha grew defensive when asked about the suspension at a news conference he held at a defense trade show.

“What’s that got to do with me?” he asked. “What do you think, I’m supposed to oversee these companies? That’s not my job. That’s the Defense Department’s job.”

Asked whether he had a lawyer, Murtha responded, “What kind of question is that?” and then ended the brief news conference by turning around and walking out of the room, accompanied by aides.

Murtha has collected more than $2 million in campaign contributions from PMA’s lobbyists and the companies the firm has represented since 1989, while Visclosky has collected more than $1 million, according to Federal Election Commission records.

The latest inquiry represents only the latest round of legal troubles for Congress involving earmarks, federal money lawmakers direct to their home states. In recent years, two former Republican congressmen have gone to prison over influence-peddling charges connected with the practice. Once-prominent Washington lobbyist Jack Abramoff, also in prison, once dubbed the earmarking committees “the favor factory.”

PMA was founded by Paul Magliocchetti, who became a lobbyist in 1989 after leaving his Capitol Hill job as a staffer on Murtha’s subcommittee. A former Visclosky chief of staff also joined PMA.

Though Murtha has long been a target of critics of so-called pay-to-play politics, Visclosky has studiously maintained a low profile. Though he hails from northwestern Indiana, an area notorious for local corruption, Visclosky has cultivated an image of being above the fray.

Even as the fallout from PMA Group has threatened to taint him, Visclosky has tried to set himself apart from other recipients of PMA’s largesse, notably Murtha and Rep. Jim Moran, a Virginia Democrat, who has received nearly a million dollars in campaign donations from employees of PMA and their clients.

Earlier this year, Visclosky joined a Republican-led effort to have the House ethics committee investigate PMA Group, a move that was destined to fail because of overwhelming Democratic opposition. Visclosky also agreed to return at least $18,000 in campaign cash from donors who were listed as having ties to PMA Group, a step Murtha and Moran have not taken.

Earlier this year, Visclosky disclosed that he had hired an attorney to represent him in the ongoing investigation.

Visclosky has deep ties to PMA. The firm employed his former congressional chief of staff and one out of every five dollars in political donations to Visclosky over the past seven years has come from PMA and its clients. He is also the leading recipient in Congress of donations from PMA employees.

Federal investigators have been looking into allegations that PMA helped funnel money to lawmakers through so-called straw donors.

The grand jury’s document subpoena to Visclosky’s congressional office could become a legal issue, as it is in the scheduled trial of former Louisiana Rep. William Jefferson, D-La. A federal appeals court in Washington ruled that the way in which a raid of Jefferson’s congressional office was conducted did not fully protect Jefferson’s privileges as a congressman. Jefferson’s lawyer says all the documents obtained in the raid should therefore be barred at his trial in June.