Salvage crews headed to a damaged jet fuel tanker off the coast of England on Tuesday, a day after it was hit by a container ship in an unexplained collision that has raised concerns of an environmental disaster.

Collision area has massive populations of seabirds, such as puffins and gannets, while porpoises and seals breed nearby

U.S.-based maritime management firm Crowley, which operates the Stena Immaculate, said the tanker “sustained a ruptured cargo tank containing Jet-A1 fuel,” when the container ship struck it, triggering a fire and “multiple explosions onboard,” with fuel released into the sea. It said all 23 mariners on the tanker were safe and accounted for.