The low intensity explosive wrapped in a plastic bag went off, shattering a portion of the ceiling and damaging some tube lights of the parking lot in the Gadkari Rangayatan, Thane Police Commissioner Anil Dhere said.

"It seems to be a deliberate act of mischief," Dhere said.

The explosion came within four days after the recovery of a low intensity explosive devise in Vashi's Vishnudas Bhave auditorium, a day ahead of the IPL finals at the D Y Patil Stadium in nearby Nerul in Navi Mumbai.

The explosive at Vashi, which was made up of gelatin sticks, was defused.

Deputy Chief Minister R R Patil got in touch with Thane police officials who informed him that a police team has already reached the site to ascertain the nature of the blast, sources in the state Home Department said.

The bomb was suspected to be planted on a bicycle in the parking lot.

Among those injured were four employees of the theatre who tried to remove the plastic bag kept on the bicycle, which triggered the explosion.

They have been admitted to the local hospital and said to be out of danger.