An oil tanker loaded with 1.5 million tons of fuel has sunk, triggering fears of a major environmental disaster – with a dramatic picture showing the exact moment it capsizes.

The Terra Nova, which has a gross tonnage of 110,720, ran into trouble in Manila Bay in the Philippines early this morning after being lashed by huge waves.

The coast guard is currently trying to determine whether the vessel was leaking oil, with after 16 of 17 crew members in a nighttime operation, officials said.

The tanker left Bataan province en route to the central province of Iloilo with industrial fuel oil stored in watertight tanks when it began taking on water.

The crew struggled to steer the tanker back to port but it eventually sank shortly after midnight, coast guard spokesperson Rear Admiral Armando Balilo said, citing statements from surviving crew members.

The sinking followed days of monsoon rains, exacerbated by a passing offshore typhoon which caused landslides and floods across the archipelago, leaving at least 22 people dead and displacing more than half a million people.

An aerial survey spotted an oil spill about 2.3 miles long near the rough seawaters where the tanker sank but that may have come from the fuel intended to power the tanker’s engine, not the much greater amount of fuel the Terra Nova was carrying as cargo, Mr Balilo said.

A coast guard ship, the BRP Melchora Aquino, was in the waters where the tanker sank, more than four miles from Bataan province’s coast, to search for the last missing crewman and to carry out an initial assessment of the tanker’s fuel oil cargo, Balilo told an online news conference.

He added that the coast guard was bracing to contain a possible major oil spill.

Nevertheless, Mr Balilo warned: “There’s a big danger that Manila would be affected, its shorelines, if the fuel leaks because this happened within Manila Bay. It’s part of the contingency we’re preparing for.

“The effect on the marine environment would not be good.”

Balilo compared the magnitude of the possible oil spill to one caused by the sinking of another Philippine oil tanker, which was carrying much less fuel oil cargo, in February last year off Oriental Mindoro province north of Manila.

That spill took about three months to contain, caused massive damage to coral reefs and mangroves in a region known for its rich biodiversity, and affected tens of thousands of fishermen and beach resorts in at least six provinces.

Manila’s shoreline is a major tourism and business hub, where the main seaport, a historic public park, the US Embassy and upscale hotels and restaurants are located.

Land reclamation efforts are also underway in the bay to create space for entertainment and tourism complexes with casinos.

The bay for years has been notorious for its pollution but famous for its picturesque sunsets.

The United States and Japan helped the Philippines with the last major oil spill’s massive cleanup and rehabilitation efforts.