Alexandria Police Chief Charles T. Strobel said yesterday he is satisfied that only one police officer was involved in a 1975 cover-up of sexual bribery allegations against former chief prosecutor William L. Cowhig.

But Strobel also said his findings were partially based on the results of a polygraph test given to a key figure in the probe, which the police chief admitted above "inconclusive."

Details of that polygraph test, given to Virginia inmate Daniel Chenault, were released yesterday in a two-page police report. According to Strobel, the internal investigation is over.

"I feel very satisfied with the probe," Strobel said yesterday. "We wanted to check out the allegations that surfaced. As far as I'm concerned it's over."

The report stems from an internal investigation by Alexandria police of the meeting-during which the allegations of sexual misconduct by Cowhig four years ago. Sherry Chenault, whose husband Daniel was awaiting trial on drug charges at the time accused Cowhig of soliciting a sexual favor in exchange for a recommendation of leniency for her husband.

One high-ranking police offier, Capt. Norman Grimm resigned from the force last month, saying he alone was responsible for covering up a damaging police polygraph report taken voluntarily by Cowhig. Grimm's resignation ended the 7-month internal probe.

But the investigation was reopened last month after Daniel Chenault told a Washington Post reporter that more than one police officer may have been aware of the earlier police investigation of Cowhig.

Chenault said that on June 3, 1975, he was taken from his city jail cell to Grimm's office in police headquarters for a meeting. According to Chenault, the meeting-during which the allegations against Cowhig were discussed-was attended by at least one other police officer.

But Strobel said in the report released yesterday that Grimm "adamantly denies the alleged meeting with Chenault."

Strobel also said that Chenault recently had been given a lie detector test and although the results were inconclusive because the polygraph machine broke down, Chenault's "breathing tracings appear to have reactions indicative of deception."

The report states that "before he would positively say Mr. Chenault was untruthful" the examiner wanted to "do further examinations." But Chenault, according to the report, refused to take a second examination.

Chenault's attorney, Roger Amole, declined to comment.

However, it was learned that Chenault was advised by Amole not to submit to another examination because of statements reportedly made by an Alexandria police investigator during the examination.

According to sources familiar with the polygraph test, the investigator told Chenault that his statements were "inconsistent" with his wife's story prior to the administration of the test.

City Councilman Donald C. Casey, who had called for a complete investigation of Chenaults story, expressed disbelief over yesterday's report.

"I think they (the police) just don't know what they're doing," Casey said.