Three U.S. technical experts involved in monitoring Soviet nuclear blasts have been relieved of their duties after the Soviets found them trying to make off with "souvenirs" from an atomic test site, administration spokesmen said Friday.

The spokesmen, dismissing the episode as a "misunderstanding," said the items found by Soviet authorities in crates being prepared for shipment back home included a small hammer, a piece of barbed wire, and several rock and core samples from a hole being drilled at the site.The July 17 incident occurred near Semipalatinsk, in south-central Russia. A U.S.-Soviet agreement allows each country to observe and monitor each other's nuclear blasts. The U.S. experts were at the site in advance of a planned explosion in September.

State Department spokesman Charles Redman said that after consultations with Soviet authorities, it was decided that the three, who were not identified, will not be returning to the testing site next month.

One was said to be an Energy Department employee, and the other two reportedly were working under Energy Department contracts.

The Soviets expressed concern over the incident but no formal protest was lodged, Redman said.