The mishap took place around 1:45 pm, they said.
According to fire officials, the impact of the blast was such that three adjoining structures were damaged.
"A small manufacturing unit, a residential structure and an ice candy shop were damaged", they said.
While two persons succumbed to their injuries at the Sion hospital, two others died at the Shatabdi hospital, police said.
The injured have also been admitted to both these hospitals. The deceased have not been identified yet and further investigations are on.