NEW reports on the Fremantle Highway incident suggest there were 3783 vehicles on board the ro-ro vessel – including 498 electric vehicles – when a fire broke out last week.

The reported numbers have increased since the blaze began on 25 July. It was initially reported that the ship was carrying around 25 electric vehicles among a cargo of 2857 cars.

A report from Reuters suggests a spokesperson for “K” Line, which chartered the vessel, revealed the larger numbers on Friday (28 July).

Fremantle Highway was still burning off the coast of the Netherlands over the weekend, according to Reuters, but the blaze had become less intense.

“We have ordered three salvage vessels to the site and salvors continue their efforts to extinguish the fire and recover the situation under the command of Dutch coast guard,” vessel owner Shoei Kisen Kaisha wrote on Friday (according to a translation of its statement).

“As far as we are aware, there is no reported oil pollution due to this incident,” it wrote.

Dutch water board Rijkswaterstaat, quoted by Reuters, said the salvage company found temperatures aboard the ship had dropped sharply on Friday morning.

The fire was still burning at the time, but there was less smoke.

Reuters wrote that the lower temperatures allowed salvage company staff to briefly board the ship to attach new tow lines at the top of the vessel for better control.

The cause of the blaze is unconfirmed, but industry and insurers have previously raised concerns around the transport of lithium-ion batteries. The batteries are found in electric vehicles.

Insurers TT Club and UK P&I Club published a whitepaper last year that suggested the maritime supply chain underestimated the danger of lithium-ion batteries.

The paper emphasised the risk of battery failure and thermal runaway at sea.

Thermal runaway occurs when heat generated by the battery becomes self-sustaining, causing a rapid temperature rise that is difficult to stop, leading to explosions or fires that are difficult to extinguish.

Panama-flagged Fremantle Highway (IMO 9667344) was drifting about 17 kilometres from the northernmost Dutch coast as of 30 July.

The Panama Maritime Authority has launched an investigation into the incident, with support from the Netherlands.