The blast took place in a store room stocked with cylinders behind a hotel located near Virar railway station. Four persons were killed and 17 injured in the explosion, they said.
The cause of the explosion was not yet known, police said, adding that the injured had been admitted to Sanjeevani Hospital in Virar, a far western suburb of Mumbai.
Police suspect that cylinders had been illegally stored in the room and a probe is being carried out in the matter.