Moscow (CNN) -- A meteor streaked through the skies above Russia's southern Chelyabinsk region Friday morning, before exploding with a flash and boom that shattered glass in buildings and left hundreds of people hurt.
The number of people reporting injuries climbed to more than 500 by lunchtime, according to Vladimir Stepanov, of the National Center for Emergency Situations at the Russian Interior Ministry.
Of those, 22 are hospitalized, he told state broadcaster Russia 24.
About 270 buildings have sustained damage -- mostly broken glass -- as a result of the shock waves caused by the blast, Stepanov said, with hospitals, kindergartens and schools among those affected.
The vast majority of injuries are not thought to be serious.
Amateur video footage showed a bright white streak moving rapidly across the sky, before exploding with an even brighter flash and a deafening bang.
The state-run RIA Novosti news agency cited the national space agency, Roscosmos, as saying that scientists believed one meteoroid had entered the atmosphere, where it burned and disintegrated into fragments.
The resulting meteorites are believed to be scattered across three regions of Russia and neighboring Kazakhstan, the news agency said.
One large chunk was discovered in a lake in the Chelyabinsk region, RIA Novosti cited the Chelyabinsk governor as saying.
The explosion was centered about 50 miles (80 kilometers) from Satka city, in the Chelyabinsk region, the state-run Itar-Tass news agency reported.
A spokesman for the Emergency Ministry of Chelyabinsk earlier told CNN the explosion sparked by the meteor injured 247 people there, with nine hospitalized.
For sky watchers, the reports bring to mind the famous Tunguska event of 1908 in remote Siberia, in which an asteroid entered the atmosphere and exploded, leveling trees over an area of 820 square miles -- about two-thirds the size of Rhode Island.
About 80 million trees were felled, radiating out from the center of the blast, but no crater was left.
Friday's Chelyabinsk meteor comes on the same day that a hefty asteroid is due to charge past Earth at a pretty close range, in space terms.
Known as 2012 DA14, the asteroid is thought to be 45 meters long, about half the length of a football field.
But scientists say it will come no closer than 17,100 miles from our planet's surface.
"No Earth impact is possible," according to Don Yeomans, manager of the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory.
Those in Eastern Europe, Asia or Australia will get the best telescope-aided view, scientists said. The asteroid won't be visible to the naked eye.
CNN's Phil Black, Boriana Milanova and Alla Eshchenko reported from Moscow, and Laura Smith-Spark wrote from London. CNN's Elizabeth Landau also contributed to this report.