Thousands of Russian emergency workers went out to clear up the damage from a meteor that exploded over the Ural mountains, damaging buildings, shattering windows and showering people with broken glass.
Divers searched a lake near the city of Chelyabinsk, where a hole several metres wide had opened in the ice, but had so far failed to find any large fragments, officials said on Saturday.
The scarcity of evidence on the ground fuelled scores of conspiracy theories over what caused the fireball and its huge shockwave on Friday in the area which plays host to many defence industry plants.
Nationalist leader Vladimir Zhirinovsky told reporters in Moscow it could have been "war-mongers" in the United States. "It's not meteors falling. It's a new weapon being tested by the Americans," he said.
A priest from near the explosion site called it an act of God. Social media sites were flooded with speculation about what might have caused the explosion.
"Honestly, I would be more inclined to believe that this was some military thing," said Oksana Trufanova, a local human rights activist.
Asked about the speculation, an official at the local branch of Russia's Emergencies Ministry simply replied: "Rubbish".
Residents of Chelyabinsk, an industrial city 1,500 km east of Moscow, heard an explosion, saw a bright light and then felt a shockwave that blew out windows and damaged the wall and roof of a zinc plant.
The fireball travelling at a speed of 30 km per second according to Russian space agency Roscosmos, blazed across the horizon, leaving a long white trail visible as far as 200 km away.
NASA estimated the object was 17 metres across before entering Earth's atmosphere and weighed about 10,000 tons.
It exploded miles above Earth, releasing nearly 500 kilotons of energy - about 30 times the size of the nuclear bomb dropped on the Japanese city of Hiroshima in World War Two, NASA added.
"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 at the Jet Propulsion Laboratory in Pasadena, California.
"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."
Only small objects found
Search teams said they had found small objects up to about one centimetre wide that might be fragments of a meteorite, but no larger pieces.
The Chelyabinsk regional governor said the strike caused about one billion roubles ($NZ39 million) worth of damage.
Life in the city had largely returned to normal by Saturday although 50 people were still in hospital. Officials said more than 1,200 people were injured, mostly by flying glass.
Repair work had to be done quickly because of the freezing temperatures, which sank close to -20 degrees Celsius at night.
Emergencies Minister Vladimir Puchkov inspected the damage after President Vladimir Putin sent him to the region.
His ministry is under pressure to clean up fast following criticism over the failure to issue warnings in time before fatal flooding in southern Russia last summer and over its handling of forest fires in 2010.
Putin will also want to avoid a repeat of the criticism that he faced over his slow reaction to incidents early in his first term as president, such as the sinking of the Kursk submarine in 2000 which killed all 118 people on board.