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CHICAGO - Rep. Jesse Jackson Jr. will likely not return to Congress until after Labor Day, a senior aide close to the congressman told ABC News.

The source also denied a rumor reported on the Chicago WLS talk radio show Roe & Roeper that the Democratic congressman's mysterious absence was due to a suicide attempt. He claimed to have spoken to Jackson as recently as "the last few days," and said that although he continues treatment at an inpatient facility, the congressman is not facing any life-threatening ailments.

The source, who agreed to speak on the condition of anonymity, declined to provide any details on where Jackson is seeking treatment, but said that he is genuinely suffering from "exhaustion."

"That's what he has. He doesn't get a lot of sleep and he has sleep disorders. He's very energetic, running full-steam ahead, working six or seven days a week often and he's been doing that for a long time," the source said. "There's a great deal of pressure on him due to unfounded allegations [related to the ethics inquiry] and negative press onslaught against him that are not true, so it kinda all caught up to him. He needed downtime to get away from grind."

Nearly two weeks after Rep. Jesse Jackson's staff released a murky statement that he was undergoing "extended in-patient treatment" due to an unspecified condition, the mystery around the high-profile congressman's disappearance from Congress is growing and starting to raise the concerns of his colleagues and constituents alike.

Fellow Illinois lawmaker Dick Durbin, the Senate's number-two Democrat, said Monday that Jackson needs to update his condition "soon."

"He's clearly going through a very difficult time," Durbin said. "I don't have any inside information about his medical situation. If there is some medical necessity for him not saying more at this moment, then I will defer to that. But he will have to soon make a report on what he's struggling with, the physical condition he's struggling with.

"First and foremost, I want Congressman Jackson to get well, to come home, to be there for his family, and to be there for his district, and his health is the number one priority," he said. "As a public official though, there reaches a point when you have a responsibility to tell people what you're facing and how things are going."

It has been one month since Jackson, the son of civil rights leader Jesse Jackson, left Congress. On June 10 the congressman, who represents a district that includes a large portion of Chicago's South Side and southeast suburbs, took a medical leave of absence to seek treatment for "exhaustion." But two weeks later his office said his condition was "more serious than we thought."

"Recently, we have been made aware that he has grappled with certain physical and emotional ailments privately for a long period of time," his staff said in a statement. "At present, he is undergoing further evaluation and treatment at an in-patient medical facility. According to the preliminary diagnosis from his doctors, Congressman Jackson will need to receive extended in-patient treatment as well as continuing medical treatment thereafter."

That was the last update from Jackson's camp. His current whereabouts are unknown. Now his mysterious absence is causing concerns on Capitol Hill. Durbin said Monday that the other Illinois senator, Republican Mark Kirk released statements, photographs and even a video in the weeks and months following his stroke in late January.

"I thought Sen. Kirk's video talking about his rehabilitation answered hundreds of questions that I was facing, and I think to the satisfaction of Illinois voters told them what his current situation is and what his hopes are about recovering," Durbin said.

In recent weeks speculation has swirled about the possible reason for Jackson's absence. The congressman has endured a difficult time over the past several years. He is the target of a probe by the House Ethics Committee into possible wrongdoing in how President Barack Obama's Senate seat - now held by Kirk - was filled. Only days before he left Congress on medical leave, a former fundraiser for Jackson, Raghuveer Nayak, was arrested by the FBI on charges of paying hundreds of thousands of dollars in bribes to doctors.

In addition, Jackson has faced turmoil at home. Last year his wife Sandi revealed that Jackson had engaged in an extramarital affair. She too has yet to provide any details about her husband's condition.

"As a wife, my primary concern is that of my children. I just want to make sure that they're taken care of, provided for," she reportedly said late last month.

At an event in Chicago on Monday, Jackson's father offered no details either.

"He is under medical supervision to regain his strength," the Rev. Jesse Jackson said. "At an appropriate time he'll share with the public that which he feels they should have."

But the longer Jackson's absence continues, the more questions people have about what is really going on with the elected official.

Joseph Schwieterman, a professor at DePaul University's School of Public Service, said Jackson, as a public figure, should come clean about his situation.

"Jackson's position makes him accountable to citizens, much like corporate CEOs are accountable to shareholders. It is simply a job obligation to make his condition and whereabouts known," Schwieterman told ABC News. "The refusal to provide timely information creates a circus-like atmosphere that undermines the public trust. That's the last thing we need in Illinois right now. Jackson has a full-time job working for his constituents who have a right to know more."

One of those constituents, Bishop Lance Davis of the New Zion Christian Fellowship in Dolton, Ill., told ABC News that he is "frustrated" with the congressman's mysterious departure from Capitol Hill.

"He owes his constituents an answer as to why there's been no information for this period of time," Davis said. "It's not his call to miss votes in Washington and not inform us as to why. We elected him to represent us.

"His office puts out a statement that he took a leave of absence for exhaustion? He's had plenty of time to get rested. Then there's another statement that it's more serious than that," Davis continued. "We really do need to hear from him. If he's in drug rehab or a mental health facility, we need to hear from him. If he's getting lawyered up, we should know that. We should know what he's doing… I had a feeling that he would come up AWOL because of the circumstances surrounding him and his family and this ongoing ethics investigation.

"Just the arrogance of Congressman Jackson to say, 'I'm going to take a leave and I don't owe anyone an explanation.' That's how this is playing out," Davis said. "In any case, we deserve an answer."

Rep. Emanuel Cleaver, the chairman of the Congressional Black Caucus, was asked by a reporter today whether Jackson could return to work in Washington between two weeks and four months.

"In between what you just said," Cleaver replied.

"That's not right," fumed Davis. "It's just not right."

Jackson's absence comes at a time when the congressman is facing a re-election battle. After he defeated Debbie Halvorson in the Democratic primary in March, Jackson is poised to battle Republican opponent Brian Woodworth this fall. An aide to Jackson did not respond to a message left by ABC News.