SINGAPORE - An industrial gas supply firm was fined $340,000 while its managing director was fined $45,000 on Tuesday (Jan 26) for workplace safety lapses which led to a blast in 2015 that killed one employee and injured at least seven others.

Ms Lim Siaw Chian, who had returned to work from maternity leave a week before the tragedy on Oct 12 that year, was killed instantly.

The former Malaysian had received her Singapore citizenship just a month before she died.

Ms Lim's charred remains were found on six occasions over a two-month period after the incident and they were identified using her daughter's DNA.

Her baby was six months old at the time.

The explosion, which ripped through Leeden National Oxygen's laboratory in Tanjong Kling Road near Pioneer Road, also left at least seven wounded.

On Dec 1 last year, the company and its managing director Steven Tham Weng Cheong, now 69, were each convicted of an offence under the Workplace Safety and Health Act.

The court heard that they had failed to take measures to ensure that unsafe modified regulatory valve assemblies (RVA) were not used when testing combustible gases.

They had also failed to ensure that there was a system in place for the accurate tracking of gas cylinders.

During proceedings last year, Ministry of Manpower prosecutor Erdiana Hazlina said Ms Lim was carrying out gas analysis on a cylinder shortly before the explosion.

She was last seen touching a RVA connected to the cylinder, the court heard.

The regulatory valve assembly was found to have been modified with an unqualified welded joint, said Ms Erdiana.

She added that the welded joint had failed previously and was not prudently checked before usage prior to the incident.

"The failure at the unqualified welded joint... resulted in a leak of flammable methane-oxygen-nitrogen mix from the RVA during the testing of the cylinder," Ms Erdiana told the court.

The leaking gas mixture may have been subsequently ignited by the frictional heat generated due to the escaping gas mixture.

The ensuing blaze engulfed the ground-floor laboratory.

In 2016, then State Coroner Marvin Bay found that Ms Lim's death to be an industrial misadventure.

For committing the offence under the Act, a company can be fined up to $500,000 while a person can be jailed for up to two years and fined up to $200,000.

The case involving Gary Choo Pu Chang, 63, the executive director of Leeden National Oxygen at the time of the incident, is still pending. His pre-trial conference will be held on Feb 19.