MOSCOW, September 20. /TASS/. The Russian Emergencies Ministry has specified that two rescue workers were killed and four were injured after a secondary collapse occurred at a residential building in the Moscow Region city of Balashikha that was hit by a gas explosion in the morning, the ministry’s press service told TASS.

"Six rescue workers were trapped under the debris during a second collapse: four are under the care of medics and two died," a source said.

Eleven people were injured in the blast. One of them was hospitalized while ten are in out-patient treatment, medical services told TASS. Work to clear the debris has been suspended amid fears of a new cave-in.

A gas explosion occurred on the fourth floor of a residential building in Balashikha on Wednesday morning. As a result, three floors partially collapsed and two balconies were destroyed. The emergencies ministry says three tenants were killed.

According to technical supervision services, a gas leak may have been the cause of the blast at the nine-story residential building. "A gas leak in one of the apartments is the most likely scenario," a services’ source told TASS. Eye witnesses who TASS has talked to maintain that the gas leak came from an apartment where nobody lives.