LONDON, FEB. 19 -- British experts are studying U.S. files to see if Austrian President Kurt Waldheim was involved in the case of six British commandos who were captured in the Balkans in World War II and believed executed, Prime Minister Margaret Thatcher said today.

In a written reply to a question in Parliament, Thatcher said copies of the U.S. files had been flown to London as part of Britain's investigation into whether Waldheim was linked in any way with the fate of the commandos.

Thatcher had announced Tuesday that Britain was looking again at the case of the commandos, who disappeared after being captured during a series of raids on the Greek islands in 1944 and 1945.

They allegedly were turned over to German Army Group E, in which Waldheim served as an intelligence officer, before disappearing. It is suspected that they were executed after interrogation, although no records of their internment or whereabouts were ever found.

Thatcher said Tuesday, "There is no evidence to substantiate a link between Dr. Waldheim and the British commandos" but the case was reopened because "we have taken the allegations concerning Dr. Waldheim very seriously."

A government spokesman said the files brought here from the United States had not previously been seen by British experts.