At least six people were killed and several feared trapped after a residential building collapsed Tuesday night in the Thane district of the western Indian state of Maharashtra. Authorities blamed torrential rainfall in the area for the collapse.

The incident occurred at about 11 p.m., local time, (1:30 p.m. EDT) in Thakurli area of the district. “We have rescued between 20 and 25 persons thus far, but fear that just as many people are trapped in the wreckage,” Dilip Gund, chief fire officer of the local Kalyan Dombivali Municipal Corporation (KDMC), said, according to Indian Express.

Fire brigade teams from nearby areas were called to the accident site for the rescue operation, India Today reported, citing Santosh Kadam, chief of the regional disaster management committee.

KDMC Mayor Kalyani Patil said that the residents of the building, which was built in 1972, were warned to vacate because it was soon to be demolished, CNN reported.

Aging and illegal structures in the state's Thane district and Mumbai have been a cause of concern for the authorities as people occupy them despite warnings. In April 2013, a building collapsed in Thane, killing 74 people and injuring over 100. Two builders were arrested and charged with culpable homicide in the case considered the district's worst incident involving the collapse of a building. Authorities also arrested 13 other people and an official enquiry revealed that the structure was illegally built on a forest land with poor quality materials.