A case of causing death by negligence and other offences was registered in connection with a tanker explosion in a company in Shahad in Thane district that killed four persons and left three injured, a police official said on Sunday.
The explosion took place on Saturday morning when the tanker was being inspected before being filled.
The Ulhasnagar police control room official said a criminal case under relevant Indian Penal Code provisions has been registered against three persons, though no arrest has been made.
The three persons comprise a member of the company's management, the tanker driver and owner, the official added.
A detailed probe is underway into the incident, he said.