Emergency officials had reported no deaths by Friday afternoon but said that 14 people had been hospitalized.
Russian experts believe the blast was caused by a 10-ton meteor known as a bolide, which created a powerful shock wave when it reached the Earth’s atmosphere, the Russian Academy of Sciences said in a statement. Scientists believe the bolide exploded and evaporated at a height of around 20 to 30 miles above the Earth’s surface, but that small fragments may have reached the ground, the statement said.
The governor of the Chelyabinsk district reported that a search team had found an impact crater on the outskirts of a city about 50 miles west of Chelyabinsk. An official from the Interior Ministry told the Russian news agency Interfax that three large pieces of meteorite debris had been retrieved in the area and that 10,000 police officers are searching for more.
A small asteroid, known as 2012 DA14, is expected to pass close to Earth later on Friday, NASA reported on its Web site. Aleksandr Y. Dudorov, a physicist at Chelyabinsk State University, said it was possible that the meteorite may have been flying alongside the asteroid.
“What we witnessed today may have been the precursor of that asteroid,” said Mr. Dudorov in a telephone interview. Video clips from the city of Chelyabinsk showed an early morning sky illuminated by a brilliant flash, followed by the sound of breaking glass and multiple car alarms. Meteorites typically cause sonic booms as they enter the Earth’s atmosphere. On Friday, the force was powerful enough to shatter dishes and televisions in people’s homes.
“I saw a flash in the window, turned toward it and saw a burning cloud, which was surrounded by smoke and was going downward — it reminded me of what you see after an explosion,” said Maria Polyakova, 25, head of reception at the Park-City Hotel in Chelyabinsk, which is 950 miles east of Moscow. A video made outside a building in Chelyabinsk captured the astonished voices of witnesses who were uncertain what it was they had just seen.
“Maybe it was a rocket,” said one man, who rushed outside onto the street along with his co-workers when the object hit, far out of sight. A man named Artyom, who spoke to the Moscow FM radio station, said the explosion was enormous.
“I was sitting at work and the windows lit up and it was as if the whole city was illuminated, and I looked out and saw a huge streak in the sky and it was like that for two or three minutes and then I heard these noises, like claps,” he said. “And then all the dogs started barking.”
He said that there was a blast that caused balconies to shake and windows to shatter. He said he did not believe it was a meteorite. “We are waiting for a second piece, that is what people are talking about now,” the man said.
The object was visible from the city of Nizhniy Tagil, around 220 miles north of Chelyabinsk, where so many people called an emergency assistance number that it stopped working, the Novy Region news service reported.
The government response on Friday was huge. Seven airplanes were deployed to search for places where meteorites might have fallen and more than 20,000 people dispatched to comb the area on foot, according to the Ministry of Emergency Situations. There were also 28 sites designated to monitor radiation. No unusual readings had been detected, the ministry reported.
The area around Chelyabinsk is also home to “dozens of defense factories, including nuclear factories and those involved in production of thermonuclear weapons,” said Vladimir Lipunov, an astrophysicist at the Shternberg State Astronomy Institute.
“No one needs to be told what the Urals is,” Mr. Lipunov told the NTV television station. “A second hit in the same area is unlikely and everything could have been much, much worse.”
Siberia stretches the length of Asia, and there is a history of meteor and asteroid showers there. In 1908 a powerful explosion was reported near the Tunguska River in central Siberia, its impact so great that trees were flattened for 25 miles around. Generations of scientists have studied that event, analyzing particles that were driven into the Earth’s surface as far away as the South Pole. A study published in the 1980s concluded the object weighed a million tons.
In the United States, NASA alluded to the Tunguska incident when it said that it was watching closely an asteroid 150 feet in diameter expected to whiz past Earth on Friday at a distance of around 17,200 miles, the closest for many decades.
In a statement on its Web site, NASA said on Friday that there was no risk that the asteroid, 2012 DA14, would collide with Earth. But it would pass within “the belt of satellites in geostationary orbit, which is 22,200 miles above Earth’s surface.”
The asteroid is set to pass Earth at around 2:25 p.m. Eastern time, NASA said. “At the time of closest approach, the asteroid will be over the eastern Indian Ocean, off Sumatra,” the agency said.
“Asteroid 2012 DA14 will not impact Earth, but if another asteroid of a size similar to that of 2012 DA14 were to impact Earth, it would release approximately 2.5 megatons of energy in the atmosphere and would be expected to cause regional devastation,” NASA said. The asteroid will not be visible to the naked eye, the agency added.
Referring to the “Tunguska Event,” NASA said the impact of an asteroid just smaller than 2012 DA14 “is believed to have flattened about 825 square miles of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia.”
Viktor Klimenko contributed reporting from Moscow, and Alan Cowell from London.
