The State Department confirmed late Friday that the contractors who gained improper access to Barack Obama's passport files worked for two Virginia-based companies, after Secretary of State Condoleezza Rice promised a full investigation into breaches that affected all three presidential candidates.

The two contractors fired for snooping into Obama's records worked for Arlington, Va.-based Stanley Inc. Earlier this week, the 3,500-person company won a five-year, $570-million contract to support passport services at the State Department.

The other company was identified as The Analysis Corporation.

FOX News has learned that newly minted House Foreign Affairs Committee Chairman Howard Berman, D-Calif., will launch a probe into the cases, as Obama called for Congress to get involved.

At least four State Department workers were behind the violations -- Hillary Clinton and John McCain found out their files were improperly accessed not long after Rice apologized to Obama.

"When you have not just one but a series of attempts to tap into peoples' personal records, that's a problem not just for me but for how our government functions," Obama told reporters in Portland, Ore. "I expect a thorough and full investigation. It should be in conjunction with those congressional committees that have oversight function so it's not simply an internal matter."

The department's inspector general launched an investigation into the matter Thursday, and the Department of Justice has been notified.

"We do feel that the system worked, but the system isn't perfect," State Department spokesman Sean McCormack said at a briefing Friday afternoon.

Obama's campaign called the breach of his records "outrageous" when the news was brought to their attention Thursday, and even suggested political motives were behind it. His records were reportedly accessed on three separate occasions this year.

But Friday morning the case swiftly expanded, with the identities and motivations of those involved still undisclosed.

McCormack said an individual who accessed Obama's files also reviewed McCain's file earlier this year. This contract employee has been reprimanded, but not fired.

McCormack said the Clinton breach occurred in summer 2007 during a training exercise in which employees were asked to search the electronic file by entering a name. While the employees were encouraged to enter family names, one employee entered Clinton's name.

McCormack said the trainee was admonished, and "it didn't happen again."

He said Rice reached out to apologize to all three candidates.

"Senator Clinton will closely monitor the State Department's investigation into this and the other breaches of private passport information," Clinton's Senate office said in a statement.

McCormack said the Obama violations were detected by internal State Department computer checks, which flag certain records of high-profile people when someone tries to access the records improperly.

But he said senior management only just learned of the violations, and that the discovery "should have been passed up the line" to senior management earlier.

Obama spokesman Bill Burton issued a stern statement Thursday night, saying: "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. Our government's duty is to protect the private information of the American people, not use it for political purposes.

"This is a serious matter that merits a complete investigation, and we demand to know who looked at Senator Obama's passport file, for what purpose, and why it took so long for them to reveal this security breach."

McCain issued a statement saying: "The U.S. government has a responsibility to respect the privacy of all Americans. It appears that privacy was breached and I expect a thorough review and a change in procedures as necessary to ensure the privacy of all passport files."

The contract companies identified in the case both released statements Friday decrying the breaches.

The Stanley firm said it regretted the "rare occurrence" of unauthorized access of any individual's private information. When it fired the two subcontractors involved in accessing the Obama files, terminating them the day the incident was discovered, Stanley was not aware of others performing unauthorized searches of McCain or Clinton's files, the company said.

The Analysis Corp., or TAC, issued a statement late Friday saying it had been notified earlier in the day that one of its contractors had acted improperly.

"This individual's actions were taken without the knowledge or direction of anyone at TAC and are wholly inconsistent with our professional and ethical standards," wrote the company, based in McLean, Va.

Former Independent Counsel Joseph diGenova said the firings of the contract employees will make the investigation more difficult because the inspector general can't compel them to talk.

"My guess is if he tries to talk to them now, in all likelihood they will take the Fifth," diGenova said, referring to the Fifth Amendment's protection against self-incrimination.

The Associated Press contributed to this report.