The first reports about the incident were received by the emergency services at 4:44 am (21:44 GMT on Friday).
“At 3:18 am Moscow time [00:18 GMT], the fourth injured person was rescued. The search [and rescue] operation is underway,” the ministry said.
According to the public prosecutor’s office, two people may remain under the debris.
The search and rescue operation involves 71 people and 13 vehicles, the Ministry of Emergencies said.
Causes of the incident remain unknown.