WASHINGTON (AP) _ James Clark was turned down as a security risk when he tried to get a job at the CIA. Theresa Marie Squillacote was married to a known communist sympathizer, Kurt Alan Stand. So how did the two former campus radicals now accused of spying gain Pentagon security clearances?

Although the information obtained by the alleged spies appears less damaging than in past espionage cases, the question of how the government failed to detect documents suggesting a security risk in this case has emerged as a key issue.

Warning signs abounded.

One of the suspects, Clark, was refused a job at the CIA, his application stamped ``security disapproved,'' meaning that as early as 1980 the agency had discerned what it regarded as a security risk. The FBI had a 1975 report describing Clark's participation in the youth arm of the Communist Party. The military also had anti-draft statements Clark submitted to the Selective Service in the 1960s in which he pledged to ``fight to defeat U.S. imperialism'' and quoted Mao Zedong on revolution.

All this appears to have escaped the notice of government security reviewers. In 1986, Clark received a ``secret'' clearance for his work for a private firm doing contract work for the government. That gave Clark access to chemical weapons documents, including a how-to manual on the manufacture of nerve gas. He kept that clearance when he went to work for the Army as a civilian analyst in 1988, and the Army reaffirmed that clearance in 1992.

Squillacote, another of the suspects, had been married for more than a decade to Stand, a communist sympathizer and the third suspect in the alleged spy ring, when she went to work for the Pentagon in 1991. Stand allegedly recruited the others in the 1970s to spy for East Germany. In 1979, Squillacote had organized a speaking appearance at the University of Wisconsin's Milwaukee campus for a man convicted of spying for North Vietnam.

Yet in 1992, the Defense Department gave Squillacote the same ``secret'' clearance.

Thomas J. Pickard, the FBI official who supervised the probe, when asked how the wife of a known communist could get a cleared post at the Pentagon said, ``I'm not going to try to explain it.''

Court-appointed lawyers for Clark and Squillacote declined to comment Tuesday.

The Pentagon had few answers on Tuesday but said it was investigating.

``Any time you have a breach like this, it causes you to go back and see how good your security measures are,'' said Defense Secretary William Cohen. But while he said strict controls are important, ``you also have to make sure that you don't employ tactics that you end up `Stalinizing' your society.''

Navy Capt. Michael Doubleday said that secret security clearances require no background check. But they do require a review of government records, which might have turned up the FBI report and CIA job rejection on Clark and records of Stand's communist involvement.

A Pentagon review of possible security breaches has already begun, Doubleday said. It is examining ``whether there were unusual circumstances that resulted in the individuals being granted security clearances, and secondly, to see if there need to be any changes in the process.''

The CIA's rejection of Clark's job application in 1980 after the agency's own security review would not necessarily have been shared with other government agencies, according to an intelligence official familiar with the reviews. In 1980, Clark might have been turned down for a relatively minor infraction such as having smoked marijuana which, years later, might not preclude a security clearance, said the official, who spoke on condition of anonymity.

Another possible reason the warning signs were missed emerges in the FBI's 200-page affidavit: It alleges that Clark and Squillacote lied on various security clearance and job applications forms, denying any involvement in communist organizations or groups seeking the overthrow of the United States.

Whatever the reasons, the East German spy handlers who allegedly worked with the three were delighted that a cell they had nurtured from the Americans' college days in the 1970s was beginning to penetrate the government, according to the affidavit.

``That was a nice piece of work,'' one East German intelligence officer told Clark in 1988 after he went to work for the Army, according to a communication intercepted by investigators.

In late 1990, Lothar Ziemer, the East German intelligence officer who investigators say worked with the three, wrote to Squillacote, ``It was very clever and courageous how you got the internship at yur oncle's (sic) office.'' The FBI says the note was congratulating Squillacote for landing a job on the staff of the House Armed Services Committee under Rep. Les Aspin, D-Wis., the committee chairman.

Clark, though worried that federal investigators were closing in, noted with satisfaction in comments picked up by FBI bugs that his security clearance had not been pulled, investigators say. By that time, an FBI undercover operation was under way.

``It seems that someone in the former (East Germany) has fingered me,'' Clark was recorded as saying. But if authorities had evidence, they were ``not even denying me my clearance so far, not even enough to deny me my clearance.''