The fire in a local train on Central Railway at Thane station on Sunday was due to an external source, possibly a public prank, but more expert opinion is required to ascertain the cause, a joint inquiry committee report on the incident has said.

The railways had initiated a probe into the incident. “During observation and demo it was found that air inlet filters are not fire retardant. The CCTV footage was also examined. After observation, it was found that the fire initiated in the upper filter possibly from an outside source. As the said coach was occupied by passengers, expert opinion is required to ascertain the source of fire,” the report added.