(CNN) -- The State Department said Friday that all three presidential candidates' passport files were breached.
Sen. Barack Obama's passport file was breached three times since January, the State Department said.
The admission comes after it was revealed Sen. Barack Obama's files had been viewed three times by contractors. One of the contractors also viewed the files of Republican Sen. John McCain, said State Department spokesman Sean McCormack.
Earlier Friday, Sen. Hillary Clinton's office said that the State Department had notified it that her file had been breached in 2007.
Secretary of State Condoleezza Rice said Friday she had apologized to Obama for the unauthorized viewing of his passport file by State Department contractors.
It was unknown Friday whether Rice had apologized to Clinton and McCain.
Two contractors were fired and a third was disciplined after they accessed Obama's file, McCormack said Thursday.
Rice told also said that the breaches would be investigated.
"I told him I was sorry and I told him that I myself would be very disturbed in anyone had looked at my passport files and that, therefore, I will stay on top of this," Rice said.
"We are going to do an investigation through the inspector general," she said. "None of us want us to have a situation where any American's passport file is accessed in an unauthorized way."
Rice said "it appears that the system worked" because the unauthorized viewing was flagged, but "it should have been known to senior management."
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The State Department will brief Clinton's staff this afternoon, a statement from her Senate office said. State Department members are also briefing McCain's staff.
State Department officials said Rice was told Thursday that Obama's files had been improperly viewed and that she told her staff she wanted a full investigation.
The State Department has refused to release the names of the companies that employed the contractors.
The chairman of the House Oversight and Government Reform Committee, Rep. Harry Waxman, sent a letter to Rice asking for the companies' names and said they should be made public.
The department hires contractors to design, build and maintain their systems and help employees with searches. McCormack said two of the contractors in the Obama case were "low-level" personnel and the other was in a mid-level position with no management role.
The breach seems like "imprudent curiosity" among the contract workers, said McCormack, adding that senior management at the State Department was not aware of the incidents until Thursday afternoon. Breaches occurred January 9, February 21 and March 14.
A State Department source said passport files contain scanned images of passport applications, birth date and basic biographical information, records of passport renewal and possibly citizenship information.
Obama's campaign is asking for a complete investigation to find out who looked at his passport file and why.
"This is an outrageous breach of security and privacy, even from an administration that has shown little regard for either over the last eight years," said Obama campaign spokesman Bill Burton in a statement.
"Our government's duty is to protect the private information of the American people, not use it for political purposes."
Doug Hattaway, a spokesman for Sen. Hillary Clinton, Obama's rival for the Democratic presidential nomination, said, "If it's true, it's reprehensible, and the Bush administration has a responsibility to get to the bottom of it."
The White House declined comment Thursday evening, just hours after the State Department upper management learned of the breach.
The department would not speculate whether the information had been shared with anyone else. Watch Anderson Cooper discuss the controversy »
"That obviously is something we are investigating," said Under Secretary of State Pat Kennedy. "I have no reason to believe they did, but I certainly am not going to be dismissive of what is a serious and valid question."
Kennedy said he will brief Obama's senior staff on Friday.
Before contractors are hired, the department runs "public integrity checks," which are standard police and name checks for people who will be handling "sensitive but nonclassified information," Kennedy said.
The background checks do not include inquiries into political affiliations, Kennedy said, saying that would be "inappropriate."
A computer-monitoring system, triggered when employees access the file of a high-profile person, caught the employees, McCormack said, emphasizing that the department's system "worked."
However, despite the trigger, senior department officials only learned of the incident Thursday afternoon, after a reporter e-mailed McCormack with a question.
"It was dealt with at the office level where the incidents occurred by the office-level supervisors, who took immediate steps when they saw this," Kennedy said.
"I will admit, they failed to pass the information up the chain to a sufficiently high level." Department officials say that after Rice was told Thursday what happened, she told her staff she wanted a full investigation.
The department would not speculate on whether the information had been shared with anyone else.
"That obviously is something we are investigating," Kennedy said. "I have no reason to believe they did, but I certainly am not going to be dismissive of what is a serious and valid question."
The news was reminiscent of a breach of Bill Clinton's passport information during the 1992 presidential campaign. The FBI launched an investigation after the State Department reported that someone had ripped out pages from his passport file from the late 1960s and '70s. E-mail to a friend
