A cargo ship transporting 3,000 cars was abandoned in the middle of the Pacific Ocean on Tuesday after a massive fire broke out. As of Friday, the ship was still burning. The blaze may have been fueled by the vehicles’ lithium-ion batteries, which are notoriously difficult to extinguish once ignited.

The crew of a cargo ship carrying around 3,000 vehicles, including 800 electric vehicles, abandoned it off the coast of Alaska after a fire broke out onboard, its operator Zodiac Maritime said on Wednesday.

The U.S. Coast Guard said it would allow the fire to burn because the cars’ lithium-ion batteries could explode. The ship’s crew escaped on a lifeboat.