The United States State Department has caught three of its employees snooping on Democratic presidential frontrunner Barack Obama's passport file.
"These unauthorised accesses were detected by the State Department and they were immediately acted upon," said Under Secretary Pat Kennedy, adding that while two employees were fired, the third was disciplined.
The incidents took place on January 9, February 21 and March 14.
"We believe this was out of imprudent curiosity, so we are taking steps to reassure ourselves that that is, in fact, the case," department spokesman Sean McCormack said.
Bill Burton, a spokesman for Obama's campaign, slammed the Republican government for using the information for political purposes.
"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," he said. "Our government's duty is to protect the private information of the American people, not use it for political purposes."
"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," Burton said.
A similar data breach was reported in 1992 when State Department officials looked up data on the then presidential candidate Bill Clinton amid campaign rumours that he had sought to renounce his citizenship to escape being drafted during the Vietnam War.
McCormack said that senior management at the State Department was not aware of the incidents until Thursday afternoon.
The contract workers used their authorised computer network access to look up files within the department's consular affairs section, which processes and stores passport Information. They read Obama's passport application and other records in violation of department privacy rules.
Obama, who is locked in a close race with New York Senator Hillary Clinton for the Democratic presidential nomination, however, received some good news ahead of the April 22 Pennsylvania vote with New Mexico Governor Bill Richardson throwing his weight behind him.
Obama, who is bidding to be the first African-American candidate to be elected to the Oval office, and Clinton had been actively lobbying Richardson, who was himself a candidate but dropped out early in the race.
"Obama will be a historic and great president, who can bring us the change we so desperately need," said Richardson.
"I believe he is the kind of once-in-a-lifetime leader that can bring our nation together and restore America's moral leadership in the world," he said.
The endorsement comes as a new opinion poll showed Obama trailing in the race after controversial comments made by his pastor triggered another race row and threatened to damage his campaign.
Richardon, who served under President Bill Clinton as his energy secretary and ambassador to the United Nations, also praised Hillary as a "distinguished leader with vast experience".
Latest delegate tally showed Obama was leading with 1,610 delegates while Clinton had 1,496. A candidate must have 2,025 candidates to win the Presidential nomination at the party convention in August.