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WASHINGTON -- A scientist and his wife who both once worked at Los Alamos National Laboratory before becoming outspoken critics were arrested Friday after an FBI sting operation and charged with trying to sell nuclear secrets to Venezuela.

The scientist, Pedro Leonardo Mascheroni, is being detained until a hearing Monday morning in Albuquerque, New Mexico. His wife, Roxby Mascheroni, was released on a variety of conditions, including a monitor attached to her.

The investigation first drew attention last October when federal agents reportedly seized six computers, two cameras, two cellphones and hundreds of files from the scientist, Pedro Leonardo Mascheroni.

Mascheroni declared his innocence to The New York Times last year, saying, "If I were a real spy, I would have left the country a long time ago."

After their arrest Friday morning, the two appeared in federal court in Albuquerque, New Mexico and were accused of dealing with an FBI undercover agent posing as a Venezuelan agent. The government did not allege that Venezuela or anyone working for it sought U.S. secrets.

The pair were indicted for allegedly communicating classified nuclear weapons data to a person they believed to be a Venezuelan government official.

Accused in a 22-count indictment are Mascheroni, 75, a naturalized U.S. citizen from Argentina, and Marjorie Roxby Mascheroni, 67, a U.S. citizen. Both were formerly contract employees at Los Alamos.

According to the indictment, Mascheroni told an undercover agent he could help Venezuela develop a nuclear bomb within 10 years and that under his program, Venezuela would use a secret, underground nuclear reactor to produce and enrich plutonium, and an open, aboveground reactor to produce nuclear energy.

In July 2008, the FBI agent provided Mascheroni with 12 questions purportedly from Venezuelan military and scientific personnel.

According to the criminal charges, Mascheroni delivered to a post office box in November 2008 a disk with a coded 132-page document on it that contained "restricted data" related to nuclear weapons. Written by Mascheroni and edited by his wife, the document was entitled "A Deterrence Program for Venezuela" and it laid out Mascheroni's nuclear weapons development program for Venezuela.

Mascheroni stated that the information he was providing was worth millions of dollars, and that his fee for producing the document was $793,000, the indictment alleges.

Earlier in the investigation, Mascheroni allegedly asked the FBI agent about obtaining Venezuelan citizenship.

He told the undercover agent he should be addressed as "Luke," and that he would set up an e-mail account solely to communicate with the undercover agent, according to the indictment.

Mascheroni used the account to communicate with the agent and to arrange for deliveries of materials at the post office box used as a dead-drop location.

If convicted, the couple face up to life in prison.

Mascheroni was laid off from Los Alamos in 1988. He filed a discrimination lawsuit against the company in 1994, alleging that he lost favor with his supervisors after he sought to promote one of his projects over one that he criticized.

Over the years, he has repeatedly raised questions before Congress about the management of the nation's nuclear laboratories and arsenal and promoted his laser to ensure weapon reliability.

Fox News' Mike Levine and The Associated Press contributed to this report.