The Senate Intelligence Committee began a secret investigation "several days ago" into the mysterious death of former CIA official John A. Paisley, a spokesman said yesterday.

Paisley, a 55-year-old former CIA analyst, was found floating in Chesapeake Bay last Sunday with a bullet wound in his head and 40 pounds of scuba diver weights wrapped around his waist.

Maryland state police are investigating the death as a possible murder or bizarre suicide. Paisley's 31-foot sloop Brilling ran aground near Point Lookout, Md. Sept. 25, the day after he was last seen alive.

Police spokesman Cpl. Jerry Eiseman said yesterday that seven investigators have been assigned to the case and that detectives met yesterday with CIA officials at police headquarters in Pikesville, Md."They (the agents) were able to shed light on Paisley's CIA activities," Eiseman said.

"The CIA is working with us. Because of the motoriety of this case we want to gear up the investigation and bring this thing to a head," he said.

A source close to the investigation said yesterday that documents found in a briefcase aboard the abandoned sailboat and marked "For Internal Use Only," were removed by the CIA before the police were called in, but Eiseman said he had no knowledge of missing evidence.

"We have to rely on the fact that the CIA is telling us the truth," Eiseman said. "They told us they took nothing off the boat."

According to Paisley family attorney Terrence O'grady, the briefcase contained typed and handwritten notes on a CIA project Paisley had been working on. Five of the documents were signed for and removed by CIA representatives who were called by a friend of the family, O'Grady said.

CIA spokesman Dale Peterson yesterday denied that any papers had been taken from the briefcase, but said several documents marked "For Officials Use Only" were signed for and removed by CIA officers from Paisley's apartment at 1500 Massachusetts Ave. NW earlier this week. The papers, according to Peterson, were smiliar to the ones found in the briefcase.

Peterson would not reveal the nature of the project, but said Paisley was a specialist in Soviet military economics. Paisley retired from his post as deputy director of the CIA's Office of Strategic Research in 1974, but had been retained as a consultant, the CIA has revealed.

A Willmington (Del) Morning News account citing unnamed CIA sources this week drew a link between Paisley's death and the alleged sale of highly sensitive CIA documents to the Soviet Union earlier this year by a former CIA watch officer. The CIA has labeled the story "absurb."

Citing the news account, Sen. William Roth (D.Del) in a letter to the intelligence committee yesterday called for a full investigation "of the theft of documents on the KH-11 system, the loss of documents on any other surveillance system and the alleged murder of Mr. Paisley."

Peterson yesterday denied that Paisley was involved in work connected with the KH-11 satellite surveillance system, but said that while he was a CIA analyst Paisley "obviously had access to sources of information."

A committee spokesman yesterday declined to elaborate on the preliminary investigation, but said "We've inquiries and we hope to answer Sen. Roth's questions."

Paisley had separated from his wife recently and moved to the Northwest Washington apartment, and friends said that Paisley had been depressed about the breakup of his marriage. But Paisley's wife, Maryann, who lives in McLean, said Paisley had been "in fine spirits" lately.