Two contract employees of the State Department were fired and a third person was disciplined for inappropriately looking at Democratic Sen. Barack Obama's passport file.
State Department spokesman Sean McCormack said the department itself detected the instances of "imprudent curiosity," which occurred separately on Jan. 9, Feb. 21 and March 14. He would not release the names of those who were fired and disciplined. The three were working in separate offices within the passport system, according to State Department officials.
"We believe this was out of imprudent curiosity, so we are taking steps to reassure ourselves that that is, in fact, the case," McCormack said.
The State Department was looking into possible violations of the Privacy Act and would meet with lawyers on Friday, officials said.
Bill Burton, a spokesman for Obama's presidential campaign, called for a complete investigation.
"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," Burton said.
"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," he said.
"We briefed Senator Obama's office on this issue this afternoon," McCormack said. "That was when senior management first became aware of these incidents."
McCormack said it was not immediately clear what the contract employees may have seen in the records or what they were looking for. He said he did not know the names of the companies they worked for.
The department has informed Obama's Senate office of the breach, and a personal briefing for the senator's staff was scheduled for Friday, McCormack said.
The State Department does not check the political affiliation of its contractors, but a senior official told NBC News there was "no political motivation" to the incidents, adding that the three were low-level contract employees doing administrative work when they accessed Obama's records. This official told NBC News that he does not believe any of the accessed information was sent anywhere.
Monitoring systems are tripped when an employee accesses the records of the high-profile individual, a department official told NBC News. "When the monitoring system is tripped, we immediately seek an explanation for the records access. If the explanation is not satisfactory, the supervisor is notified."
Explaining why the contractors had access to the files, the official said: "The State Department uses cleared contractors to design, build and maintain our systems and cleared contract employees provide support to government employees and several steps of passport processing including data entry, file searches, customer service and quality control.
"Each time an employee logs on, he or she acknowledges the records are protected by the privacy act and that they are only available on a need-to-know basis," the official added.