Divers scoured the bottom of a Russian lake on Saturday for fragments of a meteorite that plunged to Earth in a blinding fireball whose shockwave injured 1,200 people and damaged thousands of homes.
The 10-tonnes meteor streaked across the Urals region on Friday just as the world braced for a close encounter with a large asteroid that left some Russian officials calling for the creation of a global system of space object defence.
The unpredicted meteor strike ground traffic to a halt in the industrial city of Chelyabinsk as residents poured out on the streets to watch the light show before hovering for safety when a sonic boom rang out directly overhead.
Shattered glass caused most of the injuries. Doctors said some sustained more serious wounds from doors that were blasted off hinges and ceiling collapses. About 50 people were recovering in hospitals early Saturday.
Officials counted 2,962 buildings ranging from hospitals and schools to regular households suffering from shattered glass and cracked walls.
"We have a special team working... that is now assessing the seismic stability of buildings," Emergencies Minister Vladimir Puchkov told residents as he inspected the damage in the central Russian city.
"We will be especially careful about switching the gas back on," he said in televised remarks.
A piece of the meteor -- called a meteorite once it hits the ground -- was believed to have plunged into the Chelyabinsk region's frozen Lake Chebarkul.
But the six divers who searched its waters for three hours on Saturday were able to finding nothing but mud and silt.
"They immediately discovered that the water's visibility was zero and that the bottom was covered with 1.5 metres (five feet) of sticky mud," a recovery team member told Russian media.
The emergencies minister stressed that no meteorite fragments had been discovered anywhere in the region so far despite some 20,000 rescuers and recovery workers being dispatched to the region on Friday.
The meteor explosion appears to be one of the most stunning cosmic events above Russia since the 1908 Tunguska Event in which a massive blast most scientists blame on an asteroid or a comet ripped through Siberia.
Scientists at the US space agency NASA estimated that the amount of energy released in the atmosphere was about 30 times greater than the force of the nuclear bomb dropped on the Japanese city of Hiroshima during World War II.
"We would expect an event of this magnitude to occur once every 100 years on average," said Paul Chodas of NASA's Near-Earth Object Program Office.
"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," he said in a statement published on the NASA website.
The drama in Russia developed just hours before an asteroid -- a space object similar to a tiny planet orbiting the sun -- whizzed safely past Earth at the unprecedented distance of 17,200 miles (27,000 kilometers).
That put it closer to the ground then some distant satellites and sent off alarm bells ringing in some Russian circles about this being the time for joint global action on the space safety front.
"Instead of fighting on Earth, people should be creating a joint system of asteroid defence," the Russian parliament's foreign affairs committee chief Alexei Pushkov wrote on his Twitter account late Friday.
"Instead of creating a (military) European space defence system, the United States should join us and China in creating the AADS -- the Anti-Asteroid Defence System," the close ally of President Vladimir Putin wrote.
The US space agency said the 2012 DA 14 asteroid's passing was "the closest-ever predicted approach to Earth for an object this large."
NASA estimates that a smallish asteroid such as the 2012 DA 14 flies close to Earth every 40 years on average while only hitting the planet once every 1,200 years.