Singapore authorities have reportedly been unable to determine the cause of a fatal fire on board a containership in March 2018.

The 15,000-teu Maersk Honam (built 2017) caught fire in the Arabian Sea in an incident that claimed the lives of five of the Singapore-flag ship’s crew.

The accident investigation report was issued this month by Singapore's Transport Safety Investigation Bureau (TSIB), according to Roose & Partners.

“The investigation identified that the most likely source of the fire was in a block of 54 containers with IMO Class 9 dangerous cargo which was stowed in No. 3 cargo hold,” the UK law firm said in its weekly casualty newsletter.

“However, they have been unable to reach a conclusion on the actual cause of the fire.”

Investigators reportedly said the blaze was highly likely to have originated from the "decomposition of dangerous cargo which generated intense heat and caused the fire to spread to other containers".

The report, which TradeWinds has not seen, is said to have included nine safety recommendations, including five to operator AP Moller-Maersk and four to the flag state.

In the aftermath of the fire, Maersk introduced new guidelines for stowing dangerous goods on its vessels including no longer stowing dangerous cargoes next to accommodation or propulsion areas.

“We appreciate the thoroughness of the investigation in identifying opportunities to further improve our emergency response towards ship fires," Aslak Ross, head of marine standards at AP Moller-Maersk, said in a statement.

Preventative measures

"We also appreciate TSIB’s recognition of the preventive measures taken by the AP Moller-Maersk and that TSIB is recognising the need to review legislation linked with the safe transport of dangerous cargo."

Ross said the main safety recommendations in the report have already implemented across the fleet over the past two years and that it will "be studying the report further to understand how to best make use of the recommendations going forward”.

AP Moller-Maersk chief technical officer Palle Laursen said in the same statement that the incident was "one of the most serious" in the history of the company.

"The magnitude and intensity of this fire made it impossible for any crew to successfully contain, making it key that we as an industry take steps to address the root cause to ensure seafarers never find themselves in a similar situation." he said.

"We hope this investigation will initiate a more holistic, industry wide approach where we address the concerns regarding containerised dangerous goods across the entire supply chain – starting at the manufacturing level and following through until the box has been safely delivered at destination to the customer.”

The ship eventually returned to service last year under the new name Maersk Halifax following repairs in South Korea at Hyundai Heavy Industries.

The stern section, comprising the engine room and main propulsion and machinery components, was found to be largely intact and it required only the fitting of a new bow section.

The casualty became shipping’s largest-ever containership general average claim, with the final insurance bill expected to run to more than $500m.