According to him, apparently a caseless explosive device had been placed on the floor at the left door of the second subway car.
"The blast moved to the first car and reached even the cabin of the engine driver which can be seen from a dent on its door," said the source.
No explosive device or its filling, which is used to increase the destructive effect, have yet been found in the place of the accident.
The source said that 22 bodies have been found in the place of the incident. "Very many fragments of the bodies are also scattered in the car and in the tunnel. We think that they belong to some more ten passengers," said the source.