SINGAPORE - The first tranche of hearings into February's explosion in Tuas ended on a poignant note on Thursday (Oct 7), when the judge referred to a partially melted rubber slipper at the scene and asked which of two workers who had died in the blast it belonged to.

A report by one of three experts at the hearing on Thursday contained a photograph taken just after the explosion.

The photo showed the debris, including the single slipper that was next to the control panel of a damaged mixer machine that has been at the centre of the inquiry.

Senior District Judge Ong Hian Sun asked: "That slipper next to the panel, who does it belong to? Marimuthu or Shohel?"

Mr Subbaiyan Marimuthu, 38, and Mr Shohel Md, 23, died following the blast that also killed their colleague, Mr Anisuzzaman Md, 29.

They died from severe burns covering 90 per cent of their body.

Mr Marimuthu and Mr Shohel were on the platform next to the machine when the explosion occurred.

The expert behind the report, Ms Jaime Lim Yin Yin, said it was not established during her investigations whose slipper it was.

Ms Lim, deputy director of the Major Hazards Department at the Ministry of Manpower, was the last of 22 people who testified after the hearings began on Sept 20.

The inquiry committee, chaired by Judge Ong, was appointed to look into the fatal explosion at the Stars Engrg workshop at 32E Tuas Avenue 11 on Feb 24.

The bulk of the first two weeks of hearings focused on the mixer machine used by the company, and the numerous red flags involving leaks, smoke and fires raised prior to the explosion.

The last week saw seven experts and investigators take the stand.

The other two experts who testified on Thursday were Emeritus Professor Chew Yong Tian from the Department of Mechanical Engineering at the National University of Singapore and Major Huang Weikang from the Fire Investigation Unit at the Singapore Civil Defence Force.

Prof Chew told the committee there was no reason for the mixer to be used as a closed system.

Mr Chua Xing Da, 37, the director of Stars Engrg, had instructed workers to close the pipes to the oil jacket of the machine to prevent oil from being lost during production.

Prof Chew said: "The temperature could have gone up to above 1,000 deg C... the pressure would have been very, very high."

Major Huang said he believes the oil could have been ignited by a variety of sources, including the mixer's overheated heating coils.

He added that flash fires after the initial explosion would likely have been caused by potato starch powders around the workshop.

Ms Lim said the majority of samples taken from the scene had traces of starch.

This included a sample taken from under a pallet, believed to have been undisturbed by firefighting operations.

The inquiry has been adjourned, and is expected to continue with a second tranche from Nov 15 to 19 to review recommendations to prevent such accidents.

Judge Ong will also forward the report to the public prosecutor if he thinks criminal proceedings should be taken against anyone in connection with the explosion.