The boiler explosion at a garment factory of Multifabs Limited in Gazipur on Monday might have occurred due to a fault in a safety device (pressure relief valve) of the boiler, according to a preliminary report of labour and employment ministry.

The inspector of the ministry, Hanif Hossain, prepared the report after visiting the spot a day after the explosion and submitted it yesterday to the office of the Chief Inspector of Boilers, a government agency under the industries ministr}'.

Quoting Khokon Kundu, the boiler maintenance manager of Multifabs Ltd, Hanif in the report said even after expiry of the boiler's licence, the authorities of the factory conducted a test run of it. At that time, they found faults in the safety device.

"Then they went for a quick fix and ran the boiler again," said Hanif, referring to the report.

On Monday evening, the boiler exploded, killing 13 workers and injuring around 50 others. A portion of the factor}' collapsed and the machinery of the factor}' got disintegrated on impact.

Hanif said there is a guideline of renewing the licence every year.

"The licence of this factor}' expired on June 24 this year. They applied to the boiler directorate earlier on Monday (the same day) for renewing the licence," said the inspector.

The inspector said the boiler exploded as there were faults in a safety device that created more pressure than the supported capacity.

To investigate the incident, the Fire Service and Civil Defence formed a five-member probe committee on Tuesday.

Akhtaruzzaman, a member of the committee, yesterday said they were looking for the boiler safety device (pressure relief valve).

"We will be able to know most of the reasons behind the explosion if we get the safety device," said Akhtaruzzaman, also the deputy assistant director of Gazipur fire service and civil defence.

Meanwhile, Rahenul Islam, additional district magistrate and chief of the eight-member fact-finding committee formed by Gazipur district administration on Monday night, yesterday said they had been investigating the incident on the basis of seven grounds - five technical and two administrative.

They had talked to 14 people till Wednesday, he added.

Prof Kamruzzaman of Dhaka University of Engineering and Technology (DUET) visited the spot on Wednesday to find out whether there were any technical faults.

He yesterday said many of the factory staff were giving wrong information to them. But after talking with several people, it was primarily learnt that the factor)' staff were trying to generate pressure by switching off the deliver}' valve.

"At one point, when it created more pressure, the boiler exploded," he added.