The emergency services have stopped cooling the exterior of stricken cargo ship Fremantle Highway with water because it threatened to become unstable, the coastguard said on Thursday afternoon.

“We have to make sure that no excess water ends up on board because that would damage its stability,” the coastguard said in a website update.

The measure is temporary and maybe resumed later in the day, the update said. “The advantages have to be weighed up against the risks that cooling the ship brings.”

The ship itself is still on fire and bellowing smoke, making it difficult to land investigators on board to check out the situation. The ship is currently some 16 kilometres north of the Wadden Sea island of Terschelling.

A tugboat is being used to keep the ship away from busy shipping lanes.

Meanwhile, German press agency DPA said on Thursday the number of cars on board the vessel had been revised upwards from almost 3,000 to 3,783. It bases the new figure on comments from Japanese shipping company K Line which owns the boat.

Ameland mayor Leo Peter Stoel said earlier he is extremely concerned about the risk of the vessel capsizing. If this happens, part of the cargo of 3,783 cars will drift toward the Wadden Islands, which are a protected environment.

Stoel said it is important to pay greater attention to the risks associated with cargo ships moving so close to the islands. “We have raised this issue before, and the dangers this shipping route brings,” he said on Wednesday evening.

Dutch shipping organisation KVNR has also called for tougher rules for the transport of electric cars by boat. The fire is thought to have started in one of the small number of electric vehicles on board.

“Last year there was a similar situation in the middle of the ocean, where the ship burned out completely and sank,” chairman Jan Valkier said.

The UN’s International Maritime Organisation is currently working on new rules but as yet it is unclear when they will be finalised.

Weeks

The coastguard said on Wednesday it could take days, or even weeks to make sure the fire on the Freemantle Highway is completely out.

The 23 crew members on board the Panamanian-flagged ship attempted to put out the fire themselves, but the blaze spread too fast. Specialised firefighters were brought in from Rotterdam but the situation had already become too dangerous by the time they arrived.

Seven of the crew jumped into the sea and were picked up by nearby ships. The remaining crew members were rescued by helicopter but one crew member was killed.