Atleast 20 persons have been severely injured in a gas cylinder explosion at a residential building in south Mumbai's Lalbaug area on Sunday morning, officials have said.

Two fire brigades and jumbo tankers were present at the site of the incident, the Brihanmumbai Municipal Corporation said, reported news agency ANI.

According to an NDTV report, the fire department said a "Level-1" (minor) fire had broken out in one of the apartments in the building which led to the gas cylinder explosion.

"Residents reported the fire at 7:23 am and it took fire officials nearly 30 minutes to put the flames out", officials said.

All the injured residents have been admitted to the hospital.