A meteor streaked across the sky and broke up Friday morning over the Ural Mountain city of Chelyabinsk, unleashing a tremendous shock wave that smashed windows, collapsed roofs and injured at least 1,200 people.

The intense flash of light was recorded on video as far away as Nizhny Tagil, nearly 300 miles to the north. The trail of the meteor was also visible in Kazakhstan, more than 80 miles to the south.

The Russian Interior Ministry said late in the day that at least 1,200 people were hurt. The Health Ministry said 48 were hospitalized.

The Russian Academy of Sciences estimated that the meteor weighed around 10 tons and was traveling at 10 to 12 miles per second (roughly 30,000 to 45,000 mph) when it disintegrated.

Searchers found a circular hole in the ice, 15 to 20 feet across, in a lake west of Chelyabinsk, and roped it off.

The meteor that passed through Russian skies on Friday was the largest to reach Earth in a century. Its explosion was brighter than the sun and powerful enough to send damaging shockwaves to the Earth’s surface. Other meteors have impacted the world in big and small ways.

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Residents of Chelyabinsk were drawn outdoors at 9:20 a.m. local time, as a double contrail stretched across the sky. Then came the bright flash, followed a few long moments later by the sound and shock of a huge explosion. Videos posted on Web sites recorded a cacophony of shattering glass, hundreds of car alarms and a considerable amount of swearing. Many of the videos were from dashboard cameras that many Russians use to document accidents.

None of the injuries was considered critical, and no deaths were reported. Doctors at one clinic told a local news Web site, 74.ru, that most of the injuries were either cuts from flying glass or concussions.

Sergei Zakharov, regional branch chairman of the Russian Geographic Society, told the Interfax news agency that three explosions occurred as the meteor blew apart.

“Judging by my observations, the fireball was flying from southeast to northwest,” he said. “A bright flare of more than 2,500 degrees [Celsius] happened before the three explosions. The first explosion was the strongest.”

According to his calculations, the blast took place about 36 to 42 miles above the ground and had the approximate force of one to 10 kilotons, Zakharov said.

Other measurements, though, placed the altitude of the explosion at about 18 miles, he said, which would put its force at 0.1 to one kiloton.

The event immediately began to generate conspiracy theories. One anti-Western member of parliament, Vladimir Zhirinovsky, claimed that the meteor was actually a U.S. weapons test.

The meteor preceded by 16 hours the close passage of an asteroid, known as 2012 DA14. The European Space Agency said the two were not connected.

While in the air, the meteor broke into several dozen large pieces, said Vladimir Puchkov, the emergency situations minister. Officials said they believed they had identified meteorite fragments on the ground in Chebarkul, about 50 miles west of Chelyabinsk. They said they had reports of additional fragments spread along a line of settlements stretching 75 miles farther west.

“Thank God no large objects fell in populated areas; however there were still people who were injured,” President Vladimir Putin said. “We need to think about how to help people — not just to think about it but do it immediately.”

The Interior Ministry said it mobilized 10,000 police to deal with the incident.

Alla Yeryomicheva, a blogger in Chelyabinsk, wrote that she was in her apartment when the dark sky suddenly grew as bright as “a July afternoon.” She looked out the window and saw the contrails but realized they were puffier and more ragged than those a plane would make.

“No sound,” she wrote. “And I thought how very strange . . . and then bang! Several times. Our windows and balconies were closed, but not tightly, and they swept open and everything that was on the windowsills was thrown into the middle of the room.”

A number of schools and hospitals, equipped with older windows, were damaged, she said.

Chelyabinsk, a city of 1.1 million people, has a high concentration of defense industries, and arsenals in its vicinity have occasionally exploded, but the meteor’s arrival appears not to have set any off. The roof on a zinc factory, however, came crashing down.

In Chelyabinsk alone, according to Putin’s statement, “more than 297 [apartment] houses, 12 schools, several social-service facilities and a number of industrial enterprises were damaged.”

The region’s governor, Mikhail Yurevich, said the biggest worry following the incident is the cold. It was 23 degrees Fahrenheit during the day Friday, with much lower temperatures forecast overnight.

“Our main task now is to preserve the heat in offices and homes where windows were shattered, to prevent the heating system from freezing,” he said.

The arrival of the meteor provoked comparisons to the Tunguska event of 1908, when an apparent meteor exploded over a remote part of Siberia — more than 1,000 miles to the east of Chelyabinsk — and flattened nearly 1,000 square miles of forest. Studies suggest that that meteor was on the order of 300 feet across when it exploded — far larger than Friday’s visitor.