Some industrial fuel oil from a capsized Philippine tanker has started to leak into Manila Bay, the coastguard said, as it races to avoid an environmental catastrophe.

The MT Terra Nova, carrying 1.4 million litres (369,840 gallons) of industrial fuel, capsized and sank off the coast of the Philippine capital, Manila.

The ensuing oil slick has now more than tripled in area, the coastguard said on Saturday, estimating it to stretch 12-14km (7.5-8.7 miles) across the bay, which thousands of fishermen and tourism operators rely on for their livelihoods.

The vessel sank in bad weather off Manila on Thursday as Typhoon Gaemi swept over the country, killing one crew member and leaving the country potentially facing its worst oil spill disaster. Sixteen crew members were rescued.

Divers inspected the hull of the vessel on Saturday and saw a “minimal leak” from the valves, coastguard spokesman Rear Admiral Armando Balilo said, adding it was “not alarming yet”.

“We’re hoping that tomorrow we will be able to start siphoning the oil from the motor tanker,” he said. “But we are preparing for the worst-case scenario.”

The ship that will carry the recovered oil is on its way to the area, he said.

The coastguard has warned that if the entire cargo leaked, it would be an “environmental catastrophe”.

Earlier, the coastguard said it could take up to seven days to complete the process, given that the ship is now resting on the sea floor under 34 metres (111 feet) of water.

Oil containment booms have been deployed in the area to contain any possible environmental impact. Three coastguard vessels were also spreading dispersants on the oil.

Green Peace Philippines called on the government to “do everything to recover the vessel and its contents immediately to prevent further damage to the marine environment and coastal communities”.

The environment group said in a statement that “the sunken tanker … is a ticking time bomb that further imperils the health, safety and livelihoods of coastal communities around Manila Bay”.

In 2023, it took months to clean up after a tanker carrying 800,000 litres (210,000 gallons) of industrial fuel oil sank off the central island of Mindoro. Another tanker sank off the central island of Guimaras in 2006, spilling tens of thousands of gallons of oil that destroyed a marine reserve and fishing grounds.