The Department of Justice said in a lawsuit filed Tuesday that cyclist Lance Armstrong was "unjustly enriched" while he used steroids to win multiple Tour de France titles.

In the formal complaint, the Justice Department said they would seek triple damages against Armstrong, who admitted earlier this year that he doped to win his seven straight titles. The U.S. Postal Service (USPS) paid some $40 million to appear as the title sponsor of Armstrong's team during six of those seven races.

"Defendants were unjustly enriched to the extent of the payments and other benefits they received from the USPS, either directly or indirectly," the complaint said, according to the Associated Press.

The Justice Department had previously announced its intention to join the lawsuit against Armstrong, brought by ex-teammate Floyd Landis. According to the government, Armstrong and his managers repeatedly insisted that the cyclist was not using steroids while being sponsored by the Postal Service.

“The Postal Service has now seen its sponsorship unfairly associated with what has been described as ‘the most sophisticated, professionalized and successful doping program that sport has ever seen,’" U.S. Attorney Ronald Machen said at the time.

"This lawsuit is designed to help the Postal Service recoup the tens of millions of dollars it paid out to the Tailwind cycling team based on years of broken promises. In today’s economic climate, the U.S. Postal Service is simply not in a position to allow Lance Armstrong or any of the other defendants to walk away with the tens of millions of dollars they illegitimately procured.”

The government needs to prove not only that Armstrong deceived them, but that the Postal Service was damaged by Armstrong's cheating.

Armstrong has been stripped of all his competitive results dating back to August 1998 and banned for life from competitive cycling.

Armstrong is also facing lawsuits from a Texas promotional company and The Sunday Times, a British newspaper that paid Armstrong half a million dollars to settle a libel lawsuit after reporting he had taken steroids.