The blast rocked the apartment complex on Monday at around 6am local time, completely collapsing one of its sections, videos from the scene show.

The disaster left at least three people dead, according to local officials. Another four, including a child, were rescued from the rubble and hospitalized with injuries.

Some 110 residents were registered as living in the apartment complex, and the fate of 79 remains unclear, Deputy Governor Oleg Klimov told reporters. In total, 48 apartments were damaged.

The tragedy was caused by a gas explosion, the regional office of the Federal Security Service (FSB) confirmed.

A woman living on the fourth floor of the building said that she was woken up by a loud bang and saw that all the windows in the apartment were shattered. She immediately detected a strong smell of burning.

“I made a wet cloth mask for my kids, quickly dressed them in warm clothes and grabbed some of my documents,” she said.

“We went out right onto the rubble. The whole section of the building was gone.”

Some 469 rescuers and 66 pieces of equipment were deployed to the scene. Additional teams, including psychiatric specialists and K-9 units, are being brought from all over Chelyabinsk Region and neighboring Bashkortostan Region.