A special prosecutor is investigating charges that more police officers may have been involved in concealing allegations of sexual bribery against former Alexandria prosecutor William L. Cowhig in 1975, according to an informed source.

One senior police official, Capt. Norman E. Grimm, has resigned -- acknowledging that he suppressed a key police report on the 1975 charges against Cowhig. In his letter of resignation, Grimm said he alone was responsible for suppressing the polygraph report in which Cowhig allegedly told a police examiner that he engaged in sexual activity with the wife of a defendant.

Grimm's resignation officially ended the internal investigation into the department's handling ot the 1975 charge against Cowhig, who was exonerated at the time.

However, it was learned that special prosecutor Claude M. Hilton has been told of a meeting between Grimm and the woman's husband, Daniel Wayne Chenault shortly after the Cowhigh polygraph was administered. According to Chenault, two other pulice officers were present at the meeting when the allegations concerning Cowhig were discussed.

Holton declined to comment yesterday on the new information, which he reportedly received from Chenault's attorney, Roger L. Amole. "I still have some people to talk to. I have to be sure I've talked with everyone," Hilton said.

Cowhig has repeatedly denied that he engaged in sexual activity with the woman, who accused the then prosecutor of soliciting the sexual favor in exchange for a recommendation of leniency for her husband.

Amole also declined to comment yesterday.

Chenault -- interviewed last week in a medium security prison camp in Fairfax County -- recalled the June 3, 1975, meeting. Chenault also recounted his wife's allegations against Cowhig and provided new information on police handling of the charges.

Chenault said he was taken from his Alexandria jail cell, where he was awaiting trial on drug charges, and brought to Grimm's office at police headquarters. According to Chenault, the 30-minute meeting was attended by two unidentified police officers.

"They were concered over the Cowhig incident and wanted to know what I would do about it. It was the day before may trial. They were worried that I might bring it out in court," he said.

Chenault said he learned of the alleged sexual bribe several days before the meeting. According to Chenault, his wife Sherry said she performed oral sodomy on Cowhig in exchange for a recommendation of leniency.

"I told them that no one believed me. No one believed my wife. I said I wasn't going to do anything about it. Grimm said, 'That's the best thing. It's better for all concerned."'

According to Chenault, Grimm also said that if the incident were made public "it would be bad for Cowhig's career."

Grimm refused last week to comment on the meeting.

Alexandria City Councilman Donald C. Casey said yesterday, "I can't believe there was just one (police officer) involved.... I think there is a likelihood that there are more. We have asked the city manager for a full report. If we are not satisfied, we will ask the police department to reopen their internal investigation."

Hilton was appointed four weeks ago to determine if criminal charges should be brought against Cowhig for "prosecutorial misconduct" or against any officials who may have concealed knowledge of the 1975 incident.

Cowhig resigned from office last month after being acquitted of two bingo-related bribery and illegal gambling charges. Special bingo prosecutor Edward J. White agreed to drop a third felony charge in exchange for Cowhig's resignation.