A local ministry official said such incidents were extremely rare and Friday’s events might have been linked to an asteroid the size of an Olympic swimming pool due to pass earth. However, the European Space Agency on its Twitter website said its experts had confirmed there was no connection.

“There have never been any cases of meteorites breaking up at such a low level over Russia before,” said Yuri Burenko, head of the Chelyabinsk branch of the Emergencies Ministry.

Russia’s Emergencies Ministry said 514 people had sought medical help, mainly for light injuries caused by flying glass, and that 112 of them were kept in hospital.

Despite warnings not to approach any unidentified objects, some enterprising locals were hoping to cash in.

“Selling meteorite that fell on Chelyabinsk!,” one prospective seller, Vladimir, said on a popular Russian auction website. He attached a picture of a black piece of stone that on Friday afternoon was priced at 1,488 roubles ($49.46).

WINDOWS BREAK, FRAMES BUCKLE

The blast at around 9.20 a.m. (0520 GMT) shattered windows on Chelyabinsk’s central Lenin Street and some of the frames of shop fronts buckled. The shockwave could be felt in apartment buildings in the city’s centre.

“I was standing at a bus stop, seeing off my girlfriend,” said Andrei, a local resident who did not give his second name. “Then there was a flash and I saw a trail of smoke across the sky and felt a shockwave that smashed windows.”

Chelyabinsk city authorities urged people to stay indoors unless they needed to pick up their children from schools and kindergartens. They said what sounded like a blast had been heard at an altitude of 10,000 metres (32,800 feet).