The administrator of the laboratory of a prominent AIDS researcher has been removed from his post and may be suspended, according to National Cancer Institute officials, because of possible criminal violations of federal conflict-of-interest rules in his dealings with drug companies.

The official, Prem Sarin, was removed last month as deputy chief of Robert Gallo's Laboratory of Tumor Cell Biology, eight days after congressional investigators requested documents detailing the NCI's relationship with two drug companies, according to a letter from an NCI official to the committee.

Sarin did not return a reporter's telephone calls yesterday. His attorney, Bruce Baird, said, "He is being fully cooperative with people at NIH who are reviewing some past activities of his, and he is absolutely confident that when all the facts are known, there will not be any allegation of wrongdoing whatever."

The Sarin inquiry, reported yesterday by the Chicago Tribune, is the latest problem besetting the laboratory. Gallo is being investigated by a scientific panel because of unresolved questions surrounding his discovery of the AIDS virus.

And last year, another laboratory scientist, Syed Z. Salahuddin, resigned from the National Institutes of Health, NCI's parent organization, and pleaded guilty to two felony charges for steering laboratory business to a Rockville company where his wife worked.

Gallo said in an interview that he was "shocked" by the allegations against Sarin, who has administered his laboratory's contracts, finances and personnel for the last 20 years.

"He's been the guy who took over the administration for me so I could concentrate on the science," he said. "He has always exemplified a high code. Yet, I can't say to you . . . that I am sure Prem didn't do anything wrong. I just don't know what happened."

Investigators with the oversight and investigations subcommittee of the House Energy and Commerce Committee have spent the last six months examining Sarin's relationships with three drug companies, according to a committee staffer.

He said Sarin testified at a hearing last April that he had represented one company, Responsif Corp. of Wisconsin, at a Food and Drug Administration hearing in 1986 and later served as a paid consultant to them.

On Dec. 13, the committee's chief counsel wrote the NCI requesting information on all "collaborations, agreements or other business relationships" between the NCI and two other drug companies, Pfizer Corp. and the German Degussa/ASTA Pharma Corp.

A committee staffer declined to give details of the investigation, saying, "There are a lot of things that concern us."

NCI officials apparently responded to the letter by launching their investigation. In a reply to the committee Dec. 28, Richard H. Adamson, acting deputy director of the NCI, wrote, "The NCI determined that Dr. Sarin may have violated the criminal conflict-of-interest statutes . . . .

"Because of the "very serious nature of the possible violations," Sarin has been "reassigned to a non-supervisory, non-managerial position," and has "received a proposal to suspend him from all duties without pay" until completion of the probe, according to Adamson's letter. The letter said Sarin had two weeks to respond to the proposed suspension.

NIH spokesmen declined to comment yesterday, saying it is illegal to discuss personnel matters.

Under current rules, NIH researchers are allowed to earn a maximum of $25,000 per year for lecturing and $25,000 per year as consultants to private companies, an NIH spokesman said. Only certain activities are allowed and must be approved in advance. No more than $25,000 can come from one company.

Gallo said yesterday that he encourages researchers in his laboratory to set up Collaborative Research and Development Agreements (CRADAs), contracts under which private companies help pay for government research, but that he discourages private consulting.

Based on interviews with his staff Wednesday, Gallo said, "Nobody in my lab is consulting for money to anybody, nor am I."