An American couple have been indicted for trying to pass nuclear weapons secrets to Venezuela.
Pedro and Marjorie Mascheroni, who were contractors at Los Alamos National Laboratory, a centre of US nuclear research, are accused of passing classified nuclear weapons data to an FBI agent whom they believed to be a Venezuelan government official.
Mr Mascheroni, a 75-year-old native of Argentina, worked as a scientist at Los Alamos from 1979 until 1988, when he was fired after criticising US nuclear research funding priorities, according to court documents.
The BBC reports that the arrests appear to be the result of an elaborate sting, designed to catch a scientist with a long history of grievances against his employers at Los Alamos.
For more than two years an undercover FBI agent, posing as a Venezuelan official, held a number of conversations with Mr Mascheroni about plans to develop a nuclear weapon.
According to the FBI, in November 2008 the physicist handed over a coded, 132-page document entitled A Deterrence Program for Venezuela.
The FBI's statement about the arrests makes it clear that it is not accusing the government of Venezuela of anything.