Four persons were killed and seven injured on Wednesday night after an explosion rocked a two-storey house in Patna, police said.

Patna (city) Deputy Superintendent of Police Arvind Kumar Gupta said witnesses reported seeing the building, in the Alamganj police station area, collapse after the deafening blast.

Senior police officials had rushed to the spot and rescue operations launched to look for missing persons in the debris. Bodies of four persons were retrieved.

Gupta said preliminary reports suggested that a LPG cylinder may have burst, but the magnitude of the blast has given rise to speculation that explosives may have been stored in the building.

Investigations are on to ascertain the exact nature of the blast.

Police patrolling was intensified and the Rapid Action Force and anti-riot vehicles pressed into serve to maintain peace in the communally sensitive areas of the city.