Montgomery County police officials say the department is investigating charges that several policemen may have cheated on promotional exams taken by more than 600 police officers in 1975.

Department spokesmen declined to disclose the scope of the inquiry or the specific nature of the allegations but one official familiar with it called it a "massive investigation" because dozens of officers are being questioned.That source and others said, however, that the inquiry is focusing on fever than half a dozen policemen, mostly high-ranking officers, who alegedly either received help from or gave help to subordinates taking the test.

The results of the tests were used in drawing up the promotional list that has been in effect since November 1975. All promotions since that time have been based on that list, said a police spokeswoman.

Police spokesman Phil Caswell said that the department's office of internal affairs began to look into th e cheating question last month "as a result of allegations brought to (its) attention by officers in the department."

He would not comment on statements made by some officers that the probe was precipitated by the announced transfer of several veteran members of the department's detective force to patrol work. According to sources in the department, some of those unhappy with the tranfers went to the office of internal affirs with the information about the alleged cheating.

Talk of a general nature about possible cheating on the 1975 test is not new. One official termed it "a continuing source of annoyance in the department" over the past two years.

The county personnel department, which administered the test in October 1975 confirmed that it had investigated allegations of cheating at the time, an investigation prompted basically in response to rumors, said personnel director Ronald Lloyd.

Since three different exams were given on three separate days, and since each exam was given more than once, the department at that time analyzed the scores from each test period to see if any "statistically significant" differences could be found that would indicate cheating. None was found, said Lloyd.

"I informed any officer who might know something about (the alleged cheating) to come forward," he said. "Of course, none did. So the matter was essentially dropped at that point. We went ahead with the promotion list because I couldn't substantiate the allegations. Nobody would say, 'Yes, so and so cheated.'"

William Hussman, the county's chief administrative officer who certified the test results, recalled that "as a group they were willing to say something was wrong, but they didn't want to give specific names. . . . So lacking people people in the department to stand up and say 'This is what happened,' I didn't find any basis for accepting the allegations."

Some police officers who were willing to talk to a reporter, but not to give their names, said that it was "generally assumed" at the time that there had been "widespread cheating." One officer said he was "glad something is finally coming out."

But other officers said nothing more serious than "locker-room talk" had occured, with officers who had taken a morning exam talking about it informally to other officers who were going to be taking the test in the afternoon.

Police spokesman Caswell said that when the office of internal affirs concludes its investigation, it will report its findings to Police Chief Robert diGrazia, who will decide what disiplinary action, if any, to take.

If charges are made, they will be administrative, not criminal, said Caswell, since cheating on a promotional exam would be a violation of the department's rules and regulations, not a violation of state or county law.

DiGrazi said that he would make the results public after the whole process is completed, but would not reveal any names since the matter is an internal one for the police department.