At least four people were killed and dozens of others remained unaccounted for early Monday after a suspected gas explosion ripped through a 10-story residential building in the Russian city of Magnitogorsk.
The apartment block partially collapsed after the blast, which occurred as many of the residents were sleeping at around 6 a.m. local time (8 p.m. ET Sunday).
Rescuers were searching for people trapped under the rubble.
The Russian Emergencies Ministry said 48 apartments were damaged after seven stories of a building collapsed.
Just 52 people out of the 120 people who lived in the collapsed block had been accounted for, Russian news agency TASS reported on Monday, quoting regional Gov. Boris Dubrovsky.
Local officials also warned that neighboring buildings could be at risk of collapsing.
Magnitogorsk is located 1,050 miles east of Moscow in the southern Urals.