PORT OF SPAIN, Trinidad and Tobago (AFP) — A massive oil spill from an overturned vessel off the coast of Trinidad and Tobago is “not under control”, Prime Minister Keith Rowley said Sunday.

The mystery vessel capsized last Wednesday in waters off the Caribbean island, having made no emergency calls, with no sign of crew, and no clear sign of ownership.

Rowley on Sunday declared a national emergency as oil leaking from the vessel affected some 15 kilometres (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,” the prime minister told journalists.

Divers have so far been unable to plug the leak.

Hundreds of volunteers have been toiling since Thursday to halt the spread of the oil, and the Government has asked for even more to lend a hand.

The leak has damaged a reef and Atlantic beaches, and residents of the village of Lambeau have been advised to wear masks or temporarily relocate.

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

Just how badly tourism will be affected remains unclear. A cruise ship carrying 3,000 people docked in Tobago on Sunday.

Dave Tancoo, an Opposition Member of Parliament, said tour operators were likely to face considerable losses at a time when they usually see peak profits.

“This opportunity was cruelly taken away from them,” he said.

Rowley said the mystery vessel might have been involved in “illicit” business, adding: “We don’t know who it belongs to. We have no idea where it came from, and we also don’t know all that it contains.”

Divers spotted the name “Gulfstream” on the craft’s side and have identified a length of cable, possibly indicating it was in the process of being towed, Rowley said.

The island’s Emergency Management Agency said there were no signs of life on the vessel, which is around 100 metres (330 feet) in length.

The agency released photos of an estimated 1,000 volunteers in protective white jumpsuits working to remove oil from beaches.

Farley Augustine, chief secretary of the Tobago House of Assembly, said the island is ready to accept help from other countries and had received offers of assistance.

Energy Minister Stuart Young, from Trinidad, travelled to Tobago and said the main island is ready to offer “any assistance that can be provided”.