In spring 1997, Los Alamos National Laboratory chose a scientist who was already under investigation as a suspected spy for China to run a sensitive new nuclear weapons program, several senior Government officials say.
The scientist, Wen Ho Lee asked that he be allowed to hire a research assistant, the officials said. Once in the new position, in charge of updating computer software for nuclear weapons, Lee hired a post-doctoral researcher who was a citizen of China, intelligence and law-enforcement officials said.
Although the Federal Bureau of Investigation had said that a wiretap on Lee, a computer expert born in Taiwan who is an American citizen, would allow the bureau to keep close tabs on him in the new position, the bureau never won approval for the monitoring, the officials said.
Now, two years later, Lee has been fired for security breaches at Los Alamos and senior Government officials say he remains a suspect in the F.B.I.'s continuing investigation of allegations that China stole nuclear secrets from America's weapons laboratories. He is under suspicion of having stolen the data for one of America's most advanced nuclear warheads.
China has denied that it engaged in nuclear espionage.
And the research assistant has disappeared. Even as the bureau tries to find him to question him, Government officials say they are wondering whether he played a role in a Chinese intelligence operation at the heart of America's nuclear weapons program.
In the midst of the furor over the Administration's handling of evidence of Chinese atomic espionage, the decisions to appoint Lee to the new post in 1997 and to allow him to hire a Chinese assistant have underscored doubts about the procedures followed by laboratory officials and the F.B.I. in the Los Alamos spy case.
The bureau, which opened a criminal investigation into the spy case in June 1996, gave its approval when Los Alamos officials decided to give Lee the new position, intelligence and law-enforcement officials say.
Administration officials said Lee's new posting was approved in part because they believed his access to information would be "controlled." "He only had access to material he already had in his head," said one official. "He couldn't see the latest stuff."
The bureau also assured laboratory officials and the Department of Energy, which owns the weapons labs, that it would keep close watch on Lee, and would seek approval for a wiretap to monitor his telephone conversations.
But officials now say the bureau's requests for a wiretap were repeatedly turned down by Justice Department officials who did not believe they had sufficient grounds to take to a Federal court to obtain such an authorization.
The hiring of the research assistant was not cleared with the bureau, officials said. "We didn't know about the hiring of the research assistant until after the fact," a senior law-enforcement official said.
Once the F.B.I. found out, agents investigated the post-doctoral assistant, officials said. The bureau did not conclude that the student, whom officials declined to name, had any intelligence connection. Los Alamos officials assured the bureau that the assistant, who had studied at the University of Pittsburgh, would be restricted to unclassified work, law-enforcement officials said, though it is unclear how closely Los Alamos officials monitored his activities.
The assistant worked with Lee from approximately May through September 1997, when he returned to the University of Pittsburgh, officials said. They said they were not sure whether the assistant, who was in the United States on a student visa, was still in the United States. The F.B.I. is still not sure whether the assistant is significant to its investigation, officials said.
The Los Alamos lab director, John C. Browne, told The Washington Post this month that in April 1997, Lee's classified computer code -- access to a network of classified information -- was taken away under the guise of the job change so he would not be tipped off that he was under investigation
But other law-enforcement and intelligence officials say the new job did give Lee continued access to classified as well as unclassified information. Some officials add that he retained access to nuclear test data and to other classified information.
The job given Lee in the spring of 1997 was to update nuclear weapons computer programming used to evaluate weapon performance. He was to update the programming codes for the weapons labs' "stockpile stewardship" initiative. That effort was part of a broad push by the national labs and the Energy Department to insure that the American nuclear weapons inventory could be safely maintained without further nuclear testing.
Los Alamos officials decided to give Lee the job because he had the most expertise in that speciality of any scientist at the lab. Officials also say they believed that passing him over for a job for which he was the most experienced candidate would have aroused his suspicions that he was under investigation.
But in September 1997, a few months after Lee was moved to the new post, the F.B.I. Director, Louis J. Freeh, told Energy Department officials that the bureau did not have enough evidence to arrest him, law-enforcement officials said.
Freeh said there was no longer any investigative reason for the Energy Department to keep Lee in a sensitive position. The department did not move Lee out of his post, or remove his security clearance, for another year, officials said.
By then, in late 1998, a select House committee investigating unauthorized transfers of American military technology to China, headed by Representative Christopher Cox, a California Republican, had been informed about the spy case. The senior Democrat on the panel, Representative Norm Dix of Washington, complained to Richardson about the lack of action on the matter.
Lee was given a polygraph, or lie-detector test, in December 1998, and he appeared to pass. Dissatisfied with the results, the F.B.I. gave him a second test in February, and officials said he was found to be deceptive. Lee was fired by Richardson on March 8.