Police are also monitoring online auction sites and social media after reports of people trying to sell what they claim to be meteorites from Friday's explosion, RIA Novosti said. Some of the sellers are asking as much as $4,000 each, state-run RT television reported.

The U.S. space agency, NASA, said the meteor released nearly 500 kilotons of energy, about 33 times more than the nuclear bomb the United States dropped on Hiroshima, Japan, in 1945.

NASA estimated the meteor's diameter at 55 feet (17 meters) and said it was the largest reported since 1908, when a meteor exploded over Tunguska in remote Siberia, destroying 80 million trees over an area of 820 square miles.

"We would expect an event of this magnitude to occur once every 100 years on average," Paul Chodas of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory said last week.

"When you have a fireball of this size, we would expect a large number of meteorites to reach the surface, and in this case there were probably some large ones."

The event was unrelated to the passage of another, larger asteroid some 17,100 miles from earth on Friday, according to scientists.