The Pentagon is investigating a report from a former U.S. military attache in Hong Kong that hundreds of American prisoners from the Korean War might have been shipped from China to Siberia 30 years ago, defense officials said yesterday.

"The department is looking into the matter raised by Mr. Delk Simpson," Pentagon spokesman Fred S. Hoffman said.

Simpson told The Washington Post that, while he was military attache in Hong Kong in 1955, he wrote a top-secret cable to the head of Air Force intelligence detailing a Chinese railroad worker's claim that he had seen 700 soldiers being taken by train from China to Siberia that year.

Simpson said he believes that the soldiers were Americans. Defense Department officials said they suspect, but are not certain, that they were French troops being repatriated after the French negotiated an end to the Indochina war in May 1954.

The Pentagon said 8,177 American servicemen from the Korean War are listed as missing and unaccounted for compared with 2,464 from the Vietnam war.

Simpson said his source was a Pole whose family had fled the Soviet Union for China. The Pole sought him, Simpson said, after leaving his railroad job at Manchouli -- also spelled Manzhouli -- where undercarriages of trains traveling from China to the Soviet Union are changed from standard-gauge to broad-gauge width. The Pole was in Hong Kong, Simpson said, on his way to live in Australia.

Simpson met with Defense Intelligence Agency officials here Wednesday to discuss his report, officials confirmed. Because Simpson no longer had the Pole's name in his file, they said, the United States will ask Australia to search records of immigrants for 1955 in hopes of identifying someone fitting the informer's description.

A Pentagon official said a search is also under way for the 1955 cable. Simpson said he has pressed government officials for years to investigate the sighting.

Simpson, a retired Air Force colonel, said the Pole told him that he was standing within 10 feet of about 700 soldiers, many of them black, who had stopped in Manchouli while the train undercarriages were modified.

Simpson said the Pole drew pictures of the way the soldiers were dressed, including sketches of chevrons that Simpson said strengthened his belief that the men were Americans captured by Chinese forces during the Korean War and sent to Siberian labor camps.

Pentagon officials said the French used black soldiers, including Senegalese troops, in Indochina fighting.

The repatriated troops could have been taken by rail from Vietnam through China and to the Soviet Union via the Trans-Siberian railroad for release to France, the officials said. They said this theory is being assessed during the search for the Pole and Simpson's letter.