Jesse Jackson Jr. in Mayo Clinic being treated for depression

FILE: March 20, 2012: Rep. Jesse Jackson Jr. thanks supporters at his election night party in Chicago after his Democratic primary. (AP)

ROCHESTER, Minn. – Illinois Congressman Jesse Jackson Jr., whose whereabouts haven't been disclosed since he mysteriously took a medical leave several weeks ago, is being treated for depression at the Mayo Clinic in Rochester, Minn., according to a statement Friday from the hospital.

Jackson is undergoing an extensive inpatient evaluation for depression and for gastrointestinal issues, according to the statement, which also provided the first details about his medical condition. But it provided no details about where the congressman, the son of civil rights leader Jesse Jackson, had previously been staying.

"Further information will be released as Congressman Jackson's evaluation proceeds," the statement said, adding that he and his family were "grateful for the outpouring of support and prayers that have been received throughout his care."

Jackson went on leave June 10, though his office didn't disclose it until weeks later and has been mum on details ever since. Initially, his office said Jackson was being treated for exhaustion. But his staff later said Jackson's condition was more serious and required inpatient medical treatment. They also said Jackson has been grappling with emotional issues.

Under mounting pressure from fellow politicians and others, his office released a statement last month from his unnamed doctor saying Jackson was receiving intensive medical treatment at a residential treatment facility for "a mood disorder."

The timing of the leave has raised questions, in part because Jackson is facing an ethics investigation in the U.S. House connected to imprisoned former Illinois Gov. Rod Blagojevich.

The House Ethics Committee is investigating allegations that Jackson was involved in discussions about raising money for Blagojevich's campaign in exchange for the then-governor appointing him to President Barack Obama's vacated U.S. Senate seat. Blagojevich is serving a 14-year prison sentence for corruption.

Jackson was not charged and has repeatedly denied wrongdoing.