Russian officials now are saying about 1,100 people were injured after a 10-ton meteor blazed across the sky and exploded miles above the ground.
Most injuries were caused by flying glass that shattered in the wake of sonic booms after the meteor blew up when it became compressed by Earth's atmosphere. There was no word on any deaths or anyone struck by fragments, but the Interior Ministry said 1,100 people sought medical care after the shock wave and 48 of them were hospitalized.
The object roared into the atmosphere around 9:20 a.m. Friday local time in Russia, or 10:20 p.m. in Pittsburgh. It is believed to have been traveling about 33,000 mph and shattered from 18 to 32 miles above the ground.
The event occurred less than a day before asteroid 2012 DA14 made the closest recorded pass of such a celestial object, about 17,150 miles from Earth. The asteroid's closest approach occurred around 2:30 p.m., Pittsburgh time.
The European Space Agency said on Twitter that its experts had determined there was no connection between the objects. Some other sources were suggesting, though, that the asteroid may be accompanied by smaller objects that could cause such an event.
"There could be, but it's highly unlikely for something only 50 meters in size," longtime astronomer Tom Reiland said of the asteroid. Minor Planet 10320 Reiland is an asteroid named for the Shaler resident.
The site of this meteor blast is about 3,000 miles west of Tunguska, which in 1908 was the site of the largest recorded explosion of a space object plunging to Earth. The blast of a comet or asteroid is estimated to have been about 10 megatons. It leveled some 80 million trees.
Residents Friday in the Chelyabinsk region, about 930 miles east of Moscow, were shocked and frightened by the meteor's bright light and explosion. The blast released several kilotons of energy above the region, the Russian science academy said. NASA said the meteor was about 49 feet wide before it hit the atmosphere, about one-third the size of asteroid 2012 DA14. The shock wave blew in more than 1 million square feet of glass, officials said.
"There was panic. People had no idea what was happening," said Sergey Hametov, a resident of the city of about 1 million. "We saw a big burst of light, then went outside to see what it was and we heard a really loud, thundering sound," he told The Associated Press by telephone.
Sonic booms often are caused by larger meteors when they enter the atmosphere because they are traveling so much faster than the speed of sound. Injuries on this scale are extraordinarily rare.
"Very seldom are there reports of injuries caused by meteorites," said Mr. Reiland, director of Nicholas E. Wagman Observatory operated by the Amateur Astronomers Association of Pittsburgh in Deer Lakes Park. "I'm not sure what the size of the object or how many pieces caused the broken glass that injured the people. My guess is that it might be once every 50 to 100 years."
Some fragments reportedly fell into a reservoir outside the town of Cherbakul, the regional governor's office said.
"Meteorites are more likely to hit water than land because it covers more of the Earth's surface. We can only guess how many above average sized meteorites like this one actually hit the Earth per year, decade or century," Mr. Reiland said.
Russian officials are beginning to study the event, hoping to learn more about the meteor.
Moscow journalist Eva Merkacheva told the Post-Gazette via email, "The Russian Federal Space Agency said the frequency of the occurrence of such objects entering the atmosphere is hard to know." Officials are "preparing to begin the study of debris falling material in the Chelyabinsk region. ... We cannot rule out anything: it could be metal, a stone meteorite and maybe even a fragment of a comet nucleus."
Some fragments fell in a reservoir outside the town of Chebarkul. The crash left a 26-foot-wide crater in the ice.
Lessons had just started at Chelyabinsk schools when the meteor exploded, and officials said 204 schoolchildren were among those injured.
Yekaterina Melikhova, a high school student whose nose was bloody and whose upper lip was covered with a bandage, said she was in her geography class when they saw a bright light outside.
"After the flash, nothing happened for about three minutes. Then we rushed outdoors. I was not alone, I was there with Katya. The door was made of glass, a shock wave made it hit us," she said.
City officials said 3,000 buildings in the city were damaged by the shock wave.
Donald Yeomans, manager of NASA's Near Earth Object Program in California, said he thought the event was probably "an exploding fireball event."
"If the reports of ground damage can be verified, it might suggest an object whose original size was several meters in extent before entering the atmosphere, fragmenting and exploding due to the unequal pressure on the leading side vs. the trailing side [it pancaked and exploded}," Mr. Yeomans said in an email to The Associated Press.
"It is far too early to provide estimates of the energy released or provide a reliable estimate of the original size," Mr. Yeomans said.
Small pieces of space debris -- usually parts of comets or asteroids -- that are on a collision course with the Earth are called meteoroids. When meteoroids enter the Earth's atmosphere they are called meteors. Most meteors burn up in the atmosphere, but if they survive the frictional heating and strike the surface of the Earth they are called meteorites.
The dramatic events prompted an array of reactions from prominent Russian political figures. Prime Minister Dmitry Medvedev, speaking at an economic forum in the Siberian city of Krasnoyarsk, said the meteor could be a symbol for the forum, showing that "not only the economy is vulnerable, but the whole planet."
Vladimir Zhirinovsky, the nationalist leader noted for vehement statements, said "It's not meteors falling, it's the test of a new weapon by the Americans," the RIA Novosti news agency reported.
Deputy Prime Minister Dmitry Rogozin said the incident showed the need for leading world powers to develop a system to intercept objects falling from space.
"At the moment, neither we nor the Americans have such technologies" to shoot down meteors or asteroids, he said, according to the Interfax news agency.
Pete Zapadka: firstname.lastname@example.org; 412-263-1857. The Associated Press contributed.