According to a report by NDTV, the security in charge of the complex has indicated that there was a short circuit.
Since this is an ongoing story more details are awaited.
Since the lockdown, Mumbai has witnessed several massive fires. In May a massive fire broke out in a residential building at the Napean Sea Road area of Mumbai on Tuesday. It turned into a level-II blaze and two women who were trapped on upper floors were rescued. Similarly later in the month fire erupted in a five-storey Fortune hotel in south Mumbai’s Marine Lines in which around 30 doctors had a narrow escape. The fire had begun l on the second floor of the Hotel and spread to the fourth floor. There were some coronavirus suspects also quarantined in the hotel apart from the doctors.