Emergency workers in Trinidad and Tobago are scrambling to clean up a massive oil spill after a mystery vessel ran aground near the Caribbean island, casting a pall over Carnival tourism.

Prime Minister Keith Rowley on Sunday declared a national emergency as oil leaking from the vessel affected some 15km (nearly 10 miles) of coastline.

“Cleaning and restoration can only begin as soon as we have the situation under control. Right now, the situation is not under control,” Rowley told journalists.

Environmental officials said the spill has damaged a reef and Atlantic beaches, a dire sign for the islands’ resorts and hotels that are the lifeline of the local economy during the Carnival season.

Divers have so far been unable to plug the leak. They spotted the name Gulfstream on the craft’s side and identified a length of cable, possibly indicating it was in the process of being towed, Rowley said.

The vessel capsized on February 7 off the coast of the Cove Eco-Industrial Park in southern Tobago, and currents have dragged it shorewards.

When sighted on Wednesday, the ship was sailing under an unidentified flag and made no emergency calls.

The island’s Emergency Management Agency said there were no signs of life on the vessel, whose cargo was initially believed to consist of sand and wood.

The spill comes at the height of the Carnival, threatening the tourist business that is crucial to the dual-island nation’s economy.