MOSCOW — Rescue workers pulled a 10-month-old baby boy alive from a partly collapsed apartment building in central Russia on Tuesday, calling him a “New Year miracle” after he survived in the rubble for more than 35 hours in freezing temperatures.

An explosion believed to have been caused by a gas leak destroyed at least 25 apartments in the 10-story building in the city of Magnitogorsk early on Monday, killing at least nine people, and dozens of other residents remained missing.

The rescue operation, which continued through the night, has been slowed by concerns that other parts of the building might come tumbling down, and the instability delayed the retrieval of one victim until Tuesday evening. The governor’s office said that the overhanging parts of a wall that threatened rescuers have been removed.

The temperature in Magnitogorsk, an industrial city at the southern end of the Urals more than 1,000 miles east of Moscow, hovers just over 1 degree Fahrenheit (minus 17 degrees Celsius) in the daytime and minus 20 Fahrenheit or lower overnight.