Racial tensions in the Prince George's County Police Department appear to have resurfaced in the face of efforts to train more blacks and negotiations between the county and black officers to change the promotional system.

The most noticeable sign of resentment is an anonymous letter sent out last month by a few officers who said they were "fed up with a small group of racist radicals blackmailing this department." The letter, sent by the group known as The Gray Line, said the organization was "nonracial" but was concerned that some of the black officers' demands were "detrimental to the welfare of the majority of this department."

While the group does not appear to have gained momentum, some of the statements in its letter are indicative of comments heard recently from other officers.

According to whites and blacks on the force, the frustrations that have built up recently have not affected the officers' ability to work together, but many of the officers agree that the grumbling is louder and that snide remarks are taking a sharper edge.

"There has always been racial tension, but it's surfacing more" in recent weeks, said one officer. For example, the officer said, some blacks have recently been questioned half-jokingly about the validilty of their entrance exam scores.

That comment refers to the charge made by three black police recruiters that Lt. Col. Thomas Davis, the department's highest ranking black, told them to change black recruits' test scores. When the matter came to light just before Christmas, Davis was forced to resign.

On another issue, Warren Holmes, a black officer who is active in the county's police union, said some whites have expressed to him their concern about demands by the Black Police Officers Association for changes in the promotional system that will put blacks in the upper ranks of the department. A popular sentiment among whites, according to Holmes, is, "What are they county officials going to give them blacks next?"

Police Chief Michael J. Flaherty said racial tension in the department poses a "minimal problem."

"I think tensions are created by the BPOA trying to get something for their membership," Flaherty said, but he added that any type of labor-related negotiations causes temperatures to rise in an organization.

In August 1983, the black officers association presented the police department with a list of desired changes, including dropping the use of senority points in determining officers' status for promotion and the placement of blacks on disciplinary and promotional boards and in specialty units such as internal affairs and special operations.

The group once suggested having a separate promotion list for blacks, but that proposal has been dropped. Officer Reginald Riley, the association's vice president, said the organization is proposing that those who pass a promotional test be listed alphabetically instead of ranked by test score, leaving the police chief to choose whomever he wants to promote.

"It's about the only system we can put in without jumping ranks," Riley said, but he added that Tom Lennon, county police union president, has not endorsed it.

No settlement has been reached on how to promote blacks to supervisory positions. Lawyers for the black officers say they may file a federal discrimination suit against the department.

A change in policy last fall involving tests at the training academy sparked yet another controversy. Davis instituted a new rule that allowed recruits to retake tests on which they had done poorly. The change in the middle of the 26-week course outraged several instructors, who demanded transfers. Three officers have been granted transfers, but Flaherty said Davis' decision to allow the make-up tests was legal.

Outside of the academy, officers mistakenly thought that only blacks had been allowed to take make-up tests, according to officers in the department.

Efforts to address racial tension and imbalances in the Prince George's police force began in earnest 10 years ago when the department entered a consent agreement with the Justice Department promising to increase the number of minority officers. At that time, the police department was criticized for the paucity of blacks and for alleged police brutality in a county where the black population was growing rapidly. Under the agreement, the department promised that each new recruit class would be 50 percent black and female.

The program has increased the number of blacks in the force from 33 in 1975 to 170 today. In the same time, the force has grown from 794 to 900 members. While many black and white officers said minorities are fairly well accepted now, blacks are concerned that only three blacks risen to sergeant.

Prince George's County Executive Parris Glendening said that changes made by the county police force during the past 10 years have taken time to show results. Part of the reason blacks have not moved along in the department, he said, is because few high-ranking slots have been available for promotion.

"The lack of these opportunities has frustrated a lot of officers, especially blacks," Glendening said. He said the scheduled retirement of 84 officers within eight months will ease the problem.