Russian police were combing the northern Siberian city of Krasnoyarsk on Friday for a three-tonne meteorite that has disappeared from under the nose of its keepers.

The giant rock was stolen from the yard of the Tunguska Space Event foundation, whose director said it was the part of meteor that caused a massive explosion in Siberia in 1908, news agency Interfax reported.

"It winds up that it disappeared back in June, when the foundation was moving out of its old building," a police spokesman told the agency.

"Our colleagues are establishing what got lost, where the rock is and why they only came to us about it now," he said.

Foundation director Yury Lavbin brought the three-tonne rock to Krasnoyarsk after an 2004 expedition to the site of the so-called "Tunguska event" -- a mysterious mid-air explosion in Siberia in 1908 that was 1,000 times more powerful than the nuclear bomb dropped on Hiroshima in 1945.

Lavbin claimed at the time to have discovered the wreckage of an alien spacecraft during the expedition.

Scientists continue to argue over the cause of the explosion, which flattened over 2,000 square kilometres (800 square miles) of Siberian forest.