Beleaguered Rep. Jesse Jackson Jr. could be implicated in a second federal investigation, according to reports today.

The Chicago Sun-Times, citing unnamed sources, is reporting that the FBI field office in Washington, D.C., is investigating “suspicious activity” related to the Illinois Democrat’s official Congressional account or his campaign’s finances.

Roll Call could not independently corroborate the report. But NBC News also reported this evening that Jackson is under investigation and that his lawyers had asked recently that he not be indicted before the election. NBC cited “law enforcement sources.”

Jackson has been questioned about his use of Congressional and campaign funds in the past.

For example, Roll Call reported in February that Jackson’s re-election committee had paid more than $12,000 for the Congressman and his wife to stay in Israel for an additional three nights after a weeklong excursion sponsored by a private interest group.

A year-end report filed by the Jesse Jackson Jr. for Congress campaign reported spending $9,273 on hotel accommodations at the King David Hotel in Jerusalem and $3,210 for a tour guide in Tel Aviv during a “CODEL in August 2011.”

The trip was not an official Congressional trip, known as a CODEL, but one paid for by the American Israel Education Foundation, the charitable arm of the pro-Israel lobbying group the American Israel Public Affairs Committee.

Campaign finance law experts told Roll Call at the time that lawmakers can use campaign funds for official officeholder expenses overseas, though without specifics it would be difficult to determine what trips might qualify.

Jackson said he was in Israel to attend additional meetings and had asked for verbal guidance from the Federal Election Commission before doing so. The trip had mistakenly been labeled a CODEL in the campaign finance filing.

“This was not a vacation for me,” Jackson said at the time.

Earlier this year, Jackson mysteriously disappeared from Washington and his office refused to say where he was, only that he was being treated for a medical problem. Subsequently, they acknowledged he was being treated for bipolar disorder at the Mayo Clinic. He is up for re-election on Nov. 6.

The House Ethics Committee currently has an open-ended probe related to allegations that Jackson offered to raise money for former Illinois Gov. Rod Blagojevich (D) in exchange for being appointed to a vacant Senate seat.

The independent Office of Congressional Ethics referred that matter to the committee in August 2009. The committee agreed to delay its inquiry while the Department of Justice prosecuted Blagojevich, who was found guilty of 17 of 20 corruption charges. The committee then picked up the probe, which is ongoing.