Andrei Zlobin of the Vernadsky State Geological Museum at the Russian Academy of Sciences in central Siberia says the stones he found in a river in 1988 may have been part of the so-called Tunguska meteorite that exploded over the area in 1908.
Although the Tunguska blast was 1,000 times more powerful than the nuclear bomb that destroyed Hiroshima in 1945, scientists have so far failed to find any fragments of the celestial body that caused it.
Some scientists believe it was an ice asteroid or comet that exploded in the atmosphere and evaporated, leaving no traces on the surface below.
But Zlobin says three stones found in the Khushmo River near the impact's site have traces of melting and indentations often formed during a meteorite's passing through the atmosphere.
The samples are still pending a chemical analysis.
Even if a link to the Tunguska event is confirmed, the samples would not necessarily disprove the ice comet theory because the comet's nucleus could have contained small stones, experts said.