The blast was so powerful that the roof of the adjoining building caved in and four vehicles were damaged.
The incident took place at Shravandhara housing society in Sasanenagar area.
The injured people have been identified as Shankar Subhash Kamthe (35) of Phursungi, Dattatrey Mahadev Waghmare (50) and Sakharam Laxman Hinge (50), both residents of Kalepadal, Hadapsar.
“Kamthe, who is the society manager, has sustained 75 per cent burn injuries and has been admitted to a private hospital in Pune city.
The other two are workers and they are recuperating in another hospital,” said senior police inspector Raghunath Jadhav, in-charge of Hadapsar police station.
He said that the explosion took place after Kathe switched on the electric pump.