At least seven people were killed and several others injured on Monday in a blast at a coal mine in the eastern Indian state of West Bengal, police said.

The blast went off at the colliery of Gangaramchak Mining Private Limited in Bhadulia block of Birbhum district, about 217 km northwest of Kolkata, the capital city of West Bengal.

According to the police, the blast occurred when a truck with a detonator came to the colliery for unloading and the detonator exploded suddenly.

"Initially five people were killed in the explosion at the coal mine, and later on two more deaths were reported, taking the death toll to seven," a police official said. "The injured were immediately rushed to a nearby hospital for treatment."  

Investigations on the cause of the blast are ongoing.