WASHINGTON (AP) _ An autopsy showed that convicted spy Larry Wu-tai Chin died of asphyxiation after tying a plastic trash bag over his head, the U.S. Marshals Service said Saturday.

Chin, a retired CIA translator who was awaiting sentencing for espionage at a suburban Virginia jail, took a plastic trash bag from a wastebasket in the facility's day room and placed it over his head, said U.S. Marshal Roger Ray.

On Friday morning, Chin was found unconscious in his cell at the Prince William-Manassas Regional Adult Detention Center with the trash bag over his head.

Paramedics who tried to revive Chin reported that a pair of shoelaces were tied around Chin's neck to secure the bag, said U.S. Marshals Service spokesman Stephen Boyle.

The autopsy indicated that Chin, convicted Feb. 7 of spying for China, died of asphyxiation. ''In all probability it was done by that plastic bag,'' Ray said.

Although Virginia authorities did not specifically rule the death a suicide, they found ''the medical results were consistent with the evidence of suicide discovered by those that found the body,'' Boyle said.

One of Chin's two sons, who spoke on condition he not be identified, said he was surprised by his father's suicide even though he had been despondent since the trial.

''During the trial, he was despondent about the way things were going,'' said the son. ''He was worried that his side of the story wasn't coming out the way he wanted it to.''

Chin was portrayed by prosecutors as a heavy gambler who parlayed his $30,000-a-year Central Intelligence Agency salary into $700,000 worth of real estate investments.

Boyle said an investigation into the death was being conducted by the U.S. Marshals Service and officials at the Manassas jail.

''A significant quantity'' of material written in Chinese by Chin was found in his cell, Boyle said. Investigators hoped to have the material translated by early next week, he said.

''Obviously writing was an important pastime,'' Boyle said.

Boyle branded as ''pure speculation'' a report published in Saturday's editions of The Washington Post that the material included a letter Chin had written to his wife, Cathy.

He said investigators were checking a report that Chin, a diabetic, had told an inmate last week that if he were given a life term, he would swallow a large quantity of sugar to induce a diabetic coma.

Chin's son said that when he last spoke to his father, about 10 days ago, ''Outwardly, he appeared find, but I knew that he must have been a little bit despondent.''

Chin was placed in the Manassas jail pending sentencing next month. The Marshal's Service contracts with local jails to hold federal prisoners. Ray said the agency does not dictate to local jails what items prisoners are allowed to keep in their cells.

''Plastic trash bags are allowed in the day room area for trash,'' Ray said. ''That's the policy of the jail there.''

Stephan Kaftan, superintendent of the Manassas facility, did not return a reporter's telephone call. His secretary said all queries about the case were being referred to the Marshals Service.

At the trial, prosecutor Joseph Aronica said that Chin, had been paid $10,000 a year by the Chinese government plus other amounts ranging up to $150,000, after he retired from the CIA in 1981. $150,000, after his 1981 retirement from the CIA.

Prosecutors said Chin, a native of China, had a spy career that spanned 30 years. Chin, who became a U.S. citizen in 1970, testified that he stole secret U.S. documents to help improve relations between then-President Nixon and Chinese Premier Chou-En-lai.

Chin, who was a translator for the CIA's Foreign Broadcast Information service, was convicted on all 17 counts of conspiracy, espionage and tax evasion. He faced a maximum sentence of life in prison and a possible fine of $2.5 million.