CHICAGO (AP) - Rep. Jesse Jackson Jr. left the Mayo Clinic on Tuesday after his second treatment for bipolar disorder there, but it remained unclear where the congressman was going or whether he planned to return to work in Washington.

Mayo spokesman Nick Hanson said Jackson left the Minnesota hospital Tuesday, but Hanson did not know where the congressman was going.

Neither Jackson's congressional spokesman, his publicist nor his father could immediately be reached for comment.

Jackson returned to the hospital in October amid reports that he faced a new federal investigation into potential misuse of his campaign finances. The Chicago Sun-Times first reported the probe, citing anonymous sources.

An FBI spokesman in Washington, Andrew Ames, told The Associated Press he could neither confirm nor deny the existence of federal investigation into Jackson.

The congressman remains under a House ethics committee investigation into his dealings with imprisoned former Illinois Gov. Rod Blagojevich.

Jackson, 47, disappeared in June, and it was later revealed that he was being treated at the Mayo Clinic for bipolar disorder and gastrointestinal issues. He returned to his Washington home in September, but went back to the clinic the next month.

His father, the Rev. Jesse Jackson, said then that his son had not yet "regained his balance."

Jackson was easily elected Nov. 6 to a ninth full term representing his heavily-Democratic Chicago area district, even though he had barely appeared in public since going on medical leave and his only campaigning was a robocall asking voters for patience. He spent election night at the clinic.

Jackson later issued a statement thanking his supporters and saying he was waiting for his doctors' OK before he could "continue to be the progressive fighter" they'd known for years.

On Tuesday, Illinois Gov. Pat Quinn became the latest elected official to urge Jackson to speak publicly about his condition. Chicago Mayor Rahm Emanuel called on Jackson on Monday to let constituents know his postelection plans.

The U.S. House was meeting Tuesday for the first time since before the election, and votes were scheduled for Tuesday night. It was not clear whether Jackson would be there.

The son of a famed civil rights leader, Jackson's name once was mentioned as a possible future Chicago mayor or senator. But his career has stumbled since he was linked to the Blagojevich corruption saga in 2009.

The House Ethics Committee is investigating reports that Jackson and his associates discussed raising money for Blagojevich in exchange for the then-governor appointing Jackson to President Barack Obama's former senate seat. Blagojevich is now imprisoned on corruption charges, including having tried to sell the seat.