SINGAPORE - A Vietnamese man linked to a case of stolen gas oil worth more than $200 million - the largest ever in Singapore - was sentenced on Thursday (Dec 19) to 5½ years' jail.

Doan Xuan Than, 47, who had worked as a tanker captain, was the second person to be dealt with in court over the offences. He pleaded guilty on Thursday to five counts of abetting to dishonestly receiving stolen property.

The first offender was another Vietnamese man, Dang Van Hanh, 38,who was sentenced to 2½ years' jail in July.

The Straits Times had earlier reported that 340,000 tonnes of gas oil had been stolen over several years in incidents dating back to 2014 from Shell's refinery in Pulau Bukom, the largest petrochemical production and export centre in the Asia-Pacific region.

The cases involving other alleged offenders, including 11 former Shell employees, are still pending.

The court heard that Than's case alone involved stolen gas oil worth more than US$5.7 million (S$7.7 million) in total.

According to him, between 2016 until his arrest in January last year, he earned between US$70,000 and US$90,000 after committing the offences.

Deputy Public Prosecutor Stephanie Chew said that Than started working for a Vietnam-based firm called Prime Shipping Corporation in 2012. He later became the captain of vessels including Prime Sun and MT Gaea.

According to court documents, Mr Tran Quang Tuan, who was then the chairman of Prime Shipping, had told Than that when he went to Pulau Bukom to legally buy gas oil, he could also purchase illegal cargo - the misappropriated gas oil - from a shore loading officer.

Payments would then be handled by Mr Tuan and Mr Nguyen Manh Cuong, a former director of a firm called Petrolimex Singapore, the court heard.

DPP Chew said Mr Tuan told Than that after selling the misappropriated gas oil, the profits would be shared among the trio and a fourth man identified as Mr Nguyen Quoc Tuan.

Mr Tuan, Mr Nguyen Manh Cuong and Mr Nguyen Quoc Tuan are still at large.

Than agreed to take part in the plan. He later liaised with two men - Koh Choon Wei, 37 and Muzaffar Ali Khan Muhamad Akram, 38, said the DPP.

The Singaporeans were working as shore loading officers with Shell at the time and their cases are still pending.

The vessel Prime Sun, captained by Than, docked at Pulau Bukom on May 18, 2016.

The DPP told District Judge Salina Ishak: "While at Pulau Bukom, the accused also agreed to purchase misappropriated gas oil from Muzaffar... A total of 1,589.7 metric tonnes of gas oil valued at US$651,029.84, which was stolen property, was therefore transferred from Pulau Bukom to Prime Sun (that day)."

Than continued committing similar offences after that and on Aug 1, 2017, a representative from Shell Eastern Petroleum alerted the police about the case.

Officers conducted an operation on Jan 7 last year and Than was arrested four days later.

For each count of abetting to dishonestly receiving stolen property, offenders can be jailed for up to five years and fined.