Frank Hanson, speaking for the Rochester, Minn., clinic, said he does not know Jackson's whereabouts, the Chicago Tribune reported. Congress was scheduled to convene late Tuesday afternoon, but a Jackson aide in his Washington office had no comment on his movements.
The Wall Street Journal said the investigation into Jackson's alleged misuse of campaign funds to decorate his home in Washington now includes his wife, Sandi. Two people familiar with the case told the Journal investigators were trying to determine if she was involved.
Jackson, D-Ill., who represents Chicago and some of its southern suburbs, was treated at Mayo for bipolar disorder, his aides said. His wife is a member of the Chicago City Council representing the 7th Ward.
Prosecutors could use the threat of charging Sandi Jackson to extract a guilty plea from the congressman, a Washington attorney said.
Barry Pollack, who is not connected to the case, said political spouses often become key players in corruption investigations.