SINGAPORE - The inquiry committee looking into the Tuas workshop blast probed the company's engineer on Friday (Oct 1) on why he did not advise his boss on safety issues even after a number of "red flags" were raised prior to the explosion.

Myanmar national Lwin Moe Tun, who oversaw the workers in the workshop, testified that there were several incidents involving the mixer machine prior to the Feb 24 blast at the unit located at 32E Tuas Avenue 11.

These included a fire that broke out on Feb 12 and multiple instances of white smoke emanating from the mixer machine's oil jacket from around August last year.

The smoke grew thicker in January this year, the 31-year-old engineer said.

Around 8.40am on the day of the explosion, a worker also informed Mr Lwin Moe Tun that there was a fire and that one of the heaters was glowing red.

Inquiry committee assessor Lucas Ng Hong Kiang noted that Mr Lwin Moe Tun was trained as an engineer and knew of these "red flags along the way".

"Why didn't you suggest to your boss to convene an investigation?" asked Mr Ng.

Mr Lwin Moe Tun responded: "My thinking is that whenever there is a problem I report (it) to the boss, and it's up to the boss to decide."

Dr Peter Nagler, also an assessor in the committee, asked the engineer why he had allowed others to handle the situation despite having received relevant training.

Mr Lwin Moe Tun had earlier told the committee that he was trained in workplace health and safety and was also a member of the company's risk management team.

He said he thought his boss, Stars Engrg sole director Chua Xing Da, would handle every risk situation.

Stars Engrg made an insulation material called fire wrap using the mixer machine. The machine heated up oil in a jacket that then heated ingredients including potato starch in the mixer component.

The explosion, which occurred at about 11.20am and injured 10 workers, is believed to have been caused when aerosols from the oil in the mixer machine were ignited.

Three workers - Mr Subbaiyan Marimuthu, 38, Mr Anisuzzaman Md, 29, and Mr Shohel Md, 23 - later died in hospital of severe burns.

Two other witnesses from Stars Engrg - general manager Desmond Chua Shi Yong, 38, and safety coordinator Sarkar Shibu, 33 - took to the stand on Friday.

The pair were not involved in the production of fire wrap at the Tuas workshop but were part of the risk management team.

They testified that the red flag incidents were not raised during meetings or in monthly briefings to the workers.

The hearing continues on Monday with expert witnesses giving evidence.