The FBI arrested a 24-year-old Navy enlisted man on espionage charges yesterday after the suspect allegedly stuffed a "top secret" document down his pants, walked past Pentagon security guards and handed the document to an undercover agent.

Lee Eugene Madsen, identified as the "special security officer" for the Pentagon's Strategic Warning Staff, was taken into custody at his Baileys Crossroads apartment about 6:15 p.m. A short time earlier, a federal grand jury in Alexandria had returned an eight-count indictment alleging that he stole government property and transmitted unauthorized classified documents.

Terrence Adamson, a Justice Department spokesman, said there was no evidence that any of the top secret documents were turned over to a foreign government.

But officials said there was great consternation in the Pentagon because of the ease with which Madsen allegedly signed the undercover FBI agent, William M. Chapin, into the sensitive office, which contains highly classified documents culled from intercepts of foreign governments' communications traffic.

The Strategic Warning Staff is run by a Central Intelligence Agency officer whose job is to advise the nation's intelligence chief, Adm. Stansfield Turner, "of impending hostile actions against the United States or its allies," CIA spokesman Herbert Hetu said. The office's responsibility is to uncover potential global trouble spots, rather than a nuclear attack, he said.

The Strategic Warning Staff is manned by representatives of the CIA, the Defense Intellignece Agency, and the military services. Security is provided by the Defense Department, Hetu said.

The indictment of Madsen is the second alleged breach of U.S. intelligence community security to become public in the last year. Last August, William Kampiles, 23, a low-level CIA officer, was arrested and charged with walking out of CIA headquarters in 1977 with a super-secret spy satellite manual and selling it to Soviet agents.

He was convicted last November and sentenced to 40 years in prison. The incident created a furor in intelligence circles because the CIA evidently did not know the manual was missing.

The indictment said the stolen documents included weekly military reviews, photo interpretation reports and documents on Soviet Union and Warsaw Pack strengths.

An FBI affidavit said the bureau became aware of Madsen when a man identified as Richard Grant Noble phoned the FBI's Alexandria office on July 26 to say Madsen had offered to sell him classified reports summarizing international movements of drugs.

The FBI told Noble to play along with Madsen, the affidavit said, and, last Wednesday, Noble -- furnished with $200 in marked money and a hidden tape recorder -- met Madsen and received eight top secret documents in return for the money.

Last Firday night Noble introduced Madsen to undercover FBI agent Chapin at a room in the Springfield Hilton, acting out a cover story that Chapin was from Florida and was interested in the narcotics intelligence reports -- apparently because he was a drug smuggler -- the affidavit continued.

The low-ranking Navy man, a yeoman third class, then discussed taking Chapin into the Pentagon "to demonstrate what he had to offer, "according to the affidavit. Chapin feigned disbelief, at which time Madsen assured Chapin that it could be done without risk and said he had taken several other individuals into his office at the Pentagon.

The FBI man then gave Madsen $500 for good faith and later that night accompanied him to the Pentagon. Chapin signed in, got a visitor's badge from two General Services Administration guards and got a tour of Madsen's office, the affidavit said.

Madsen allegedly said he had taken some documents home "for his scrapbook," and when Chapin asked what the most sensitive document in the room was, Madsen allegedly took out a top secret report entitled "USSR/Warsaw Pact General Indicator List." Madson then "proceeded to tuck the document under his vest and down his pants," carried it back out past the guards, and gave it to Chapin, according to the affidavit.

Madsen later allegedly told Chapin he would be willing to extend his enlistment for a year and give him a copy of a monthly narcotics traffic report for $10,000 each.

CIA security officers examined the documents on Saturday to verify their authenticity and classification, after which a sealed indictment was voted late yesterday afternoon by the grand jury.

Madsen could be sentenced to as long as 10 years in prison and a $10,000 fine on each of the eight felony counts in the indictment if he is convicted.

His apartment in the Woodlake Towers Apartment complex was searched last night by FBI and Naval intelligence agents. One source said Madsen lived with three male roommates.

He was held on $250,000 bond and is to be arraigned in U.S. District Court in aLexandria this morning.