WASHINGTON – An elderly physicist and his wife who once worked at the Los Alamos National Laboratory in New Mexico were arrested Friday on charges of attempting to sell “restricted data” to an undercover FBI agent posing as a top Venezuelan official trying to build an atomic bomb.

Pedro Leonardo Mascheroni, 75, a nationalized U.S. citizen from Argentina, and his 67-year-old wife, Marjorie Roxby Mascheroni, appeared in federal court in Albuquerque on charges of trying “to injure the United States” by passing classified nuclear weapons material in return for millions of dollars.

The couple worked at the laboratory over several decades, Pedro through much of the 1980s and Marjorie from 1981 until earlier this year. He was a scientist and her duties included technical writing and editing. Both of them had security clearances and access to material concerning the design, manufacture and use of atomic weapons.

Federal officials stressed that the government of Venezuela was not involved.

Nevertheless, said U.S. Attorney Kenneth J. Gonzales of New Mexico, laboratory employees must safeguard anything they learn there, even after leaving the lab. “This is absolutely necessary for our national security, and it is what the public expects,” Gonzales said.

The couple was charged in a 22-count grand jury indictment unsealed Friday. The Mascheronis were charged with conspiring to communicate restricted data to a foreign agent. Pedro also was charged with “concealing and retaining U.S. records with the intent to convert them to his own use and gain,” and Marjorie was charged with seven counts of making false statements to investigators.

Authorities gave this scenario of their case:

The investigation was launched in March 2008 when Pedro Mascheroni began speaking with an undercover FBI agent “posing as a Venezuelan government official.” Pedro said he could help that country “develop a nuclear bomb within 10 years.” Using information supplied by him, he said Venezuela could use a secret, underground nuclear reactor to harvest and enrich plutonium, and then an above-ground reactor to produce nuclear energy.

Pedro said he wanted to obtain Venezuelan citizenship, and he expected to be paid for his work. He also instructed the undercover agent to refer to him as “Luke,” and he set up a “dead drop” post office box for future communications.

In July 2008, the agent gave Pedro a list of 12 questions from Venezuelan military and scientific officials. Five months later, Pedro delivered a disk to the post office box that contained a coded 132-page document containing restricted data regarding nuclear weapons.

Titled “A Deterrence Program for Venezuela,” the primer was written by Pedro and edited by his wife. Pedro told the agent that he later could provide more details worth millions of dollars to build a bomb, and that his fee would be $793,000.

In June 2009, Pedro allegedly found another list of questions in the post office box, along with $20,000 in cash and a Virgin Island bank statement with a balance of more than $435,000 — a sign of more money to come.

A month later Pedro left a 39-page document answering the latest questions.

He wrote it, and his wife edited the material.