At least four people were killed and dozens remain unaccounted for after a suspected gas explosion triggered the collapse of a section of a high-rise apartment building in the Russian city of Magnitogorsk early on New Year's Eve.

President Vladimir Putin traveled to the city in the southern Urals later on December 31, while rescuers seached through the rubble after almost an entire entryway and attached apartments of the 10-story building came crashing down.

Putin met with local officials and went to a nearby hospital to meet with some of the injured.

"It is in the character of our people, despite New Year's festivities, to remember to think of the dead and wounded at this moment," Putin said at the hospital.

The Chelyabinsk regional government said earlier that rescue teams had managed to extract four bodies from the debris.

Local ambulance service officials said five people, including two children, were hospitalized.

Emergency Situations Minister Yevgeny Zinichev told Putin that between 36 and 40 people could be trapped under the rubble.

Regional Governor Boris Dubrovsky said seven children were among the missing.

Magnitogorsk Mayor Sergei Berdnikov told reporters that 38 people remain unaccounted for. But the regional governor, Boris Dubrovsky, who is at the site leading rescue operations, told reporters earlier that as many as 50 people might remain under the debris.

Cold weather -- close to minus 20 degrees Celsius -- plus a danger that the remaining part of the building might collapse are major challenges being faced by the rescue teams, Dubrovsky said.

Temperatures are expected to get several degrees colder overnight, and special large heaters had been brought in to try to keep any possible survivors from freezing to death as the rescue operations continue.

According to the regional government, the explosion took place at 6:10 a.m. local time in a complex of apartment buildings that was built in 1973 and houses some 1,100 people.

"We were sleeping and I woke up feeling I was falling down," said Yulia Gavrilova, a survivor. "I first thought I was dreaming it. Then I woke up for real and realized that I was standing outside. The wall was not there any longer. My mother was screaming that she couldn't breathe and my son was screaming from another corner."

The collapsed part of the building housed 110 people, of whom 15 were away at the time of the blast, the regional government said.

Sixteen people were evacuated from floors of the building not impacted by the blast and several others were able to escape the blast on their own.

Dubrovsky said later that some apartments were leased and that 120 people were housed in the collapsed part of the building.

The head of the Tajik diaspora in Magnitogorsk, Abulmajid Sharipov, told RFERL that a Tajik family of five was living in an apartment in the collapsed part of the building.

Shuhrat Ulfatov, 26, was found unconscious and hospitalized after spending more than six hours under the debris in freezing cold.

The fate of his wife and three children is unclear.

The Emergency Situations Ministry said on its website that, in all, 48 apartments from the third to the 10th floor in the building's central part were damaged by the explosion.

The Investigative Committee said it has launched a probe into the explosion and dispatched investigators from its central headquarters in Moscow to Magnitogorsk.

Magnitogorsk is located some 1,700 kilometers southeast of Moscow.

With reporting by RFE/RL's Tajik Service, TASS, Interfax, and RIA Novosti