The officer who supervised the Maryland State Police report concerning the alleged Prince George's County police "death squad" has written a letter to the county prosecutor apologizing for the public release of the report and saying that it may have contained some misrepresentations.

State's Attorney Arthur A. Marshall Jr, to whom the letter was sent by Maj. Gus Grant, said in an interview last night he considers it "mostly an attempt to correct some wordage in the report." He said he did not consider Grant's letter a "major revision of the earlier report."

Grant wrote: "It is I think most unfortunate that we were not given the opportunity to correct the unaccuracies and to place certain other matters in proper perspective before the sumary was made public." Grant earlier had disagreed with Attorney General Stephen H. Sachs' decision to order the release of the report.

Grant's letter was delivered to Marshall on Nov. 29. The county prosecutor then gave a copy of the letter to Joseph D. Vasco, the acting chief of police in Prince George's who in 1967 played a key role in the police operation that came to be known as the "Death Squad."

Vacso released his copy of Grant's letter lastnight. "It is too little too late," said Vasco. "But I do commend Major Grant for finally coming out and at least giving the impression that there were many inaccuracies and innuendoes in that report that should not be there."

The state police investigation, triggered by a series of articles in The Washington Post last February, confirmed earlier newspaper accounts of how several prince George's police officers, including Vasco, staged a series of convenience store holdups in 1967. Two of the suspected robbers were fatally shot during the holdups.

According to Grant's letter, written at Marshall's request, the state police report was unfair to Vasco because it implied that the investigation proved that Vasco planned major details of the armed robbery at a High's store in Adelphi on June 8, 1967, at which one of the robbers, recruited by police informants, was shot and killed by police.

"We have no proof of this," said Grant. "This . . . was told to us by the police informant who participated in the crime. The summary [report] may lead one to believe that our investigation proved or corroborated this particular allegation."

The former police informants who supplied the state police investigator with the details of Vasco's alleged role in the planning stages of the holdup took and passed lie detector tests, according to the report. Vasco refused to take a lie detector test.

Grant's letter mentions several other places in the state police report where "there may have been [unfair] misrepresentations."