Representatives of the State Department's security office last April searched through material seized a month earlier by area police from local male prostitution concerns that listed more than 1,000 alleged clients, according to informed government sources.

They checked every name that matched that of an employe of the department, one source said. Their subsequent investigation turned up one civil service employe who worked at the department and whose name was among the materials. He was described by one source yesterday as a middle-level employe who "did handle classified material."

A second source, familiar with the State Department's investigation, said, "There was no question of a security breach."

Last week, sources said, that employe, whose name has not been disclosed, left the department.

State Department officials yesterday refused to comment on the record about the case, citing a policy that forbids discussing personnel matters.

A spokesman said, however, that sexual preference is "not per se a condition of employment." He added that suitability for the initial hiring and continued employment of an individual by the department could depend on informing superiors of matters that "could create a compromising situation."

As for the review of the client lists, the spokesman said, "It is routine to check out one way or another" information such as that developed from the police raids.

One such raid, executed by D.C. and Arlington County police with a search warrant, took place on March 18, at a house in Georgetown that served as the headquarters for Friendly Models, alleged to be the front for a million-dollar homosexual prostitution out-call business.

Newspaper stories on the raid said that 11 boxes of business records were seized, including the names, addresses and telephone numbers of up to 1,000 individuals who were alleged to be "preferred customers." It was not clear yesterday if the list of clients examined by State Department officials came from the Friendly raid.

"Sometime in April," one source said yesterday, "the fact of the list came to the attention" of State's security personnel, "and they went to examine this list."

Stories have circulated recently in Washington that the Friendly Models and other lists of male prostitution firms' alleged clients have been offered for sale to foreign government intelligence agencies.

One former investigator recently told a New York State crime committee that such a list had been sold to a Soviet agent, but later in an interview with The Washington Post the ex-investigator said that he could not confirm that allegation.