Philippine Coast Guard (PCG) personnel collect oil sleek and sea water samples off the coast of Bataan on July 26, 2024, in this handout photo. Handout/PCG

MANILA (UPDATED) -- The Philippines postponed on Sunday the removal of fuel from a tanker that sank in Manila Bay, with fears of an environmental catastrophe growing as leaking oil reached shore for the first time.

The siphoning of the 1.4 million liters of industrial fuel oil from the vessel's hold was pushed back to Tuesday at the earliest so divers could seal nine leaking valves first, Philippine Coast Guard spokesman Rear Admiral Armando Balilo told reporters.

The tanker sank in bad weather off Manila early Thursday, killing one crew member and leaving the Philippines facing the possibility of its worst oil spill ever.

READ: Tanker carrying 1.4 million liters of oil capsizes in Manila Bay

READ: Philippine coast guard says oil leaking from sunken tanker

"An order was given to seal the valves first before the start of the siphoning operations in order to prevent further leakages," Balilo said Sunday.

"The weather remains bad out there but they have a target to finish this (sealing the valves) by tomorrow."

Balilo later told AFP the coast guard had found "small patches" of oil on the coast of the municipality of Bulakan, on the bay's north shore near Manila.

The contaminated shoreline was on the edge of a reclamation project for a future international airport, he said.

Balilo said the coast guard was also investigating a report by the environmental group Greenpeace that a "thick layer of oil" was coating the sea Sunday about four kilometers (2.5 miles) off the coast of Hagonoy municipality, near Bulakan.

The coast guard has warned that it would be an "environmental catastrophe" if the entire cargo were to leak.

It has also called for the suspension of fishing in Manila Bay to prevent people "eating contaminated fish".

The Philippines has struggled to contain serious oil spills in the past.

It took months to clean up after a tanker carrying 800,000 liters of industrial fuel oil sank off the central island of Mindoro last year, contaminating its waters and beaches and devastating the fishing and tourism industries.

Another tanker sank off the central island of Guimaras in 2006, spilling tens of thousands of gallons of oil that destroyed a marine reserve, ruined local fishing grounds and covered stretches of coastline in black sludge

The coast guard and a private salvage operator are also working to offload an unspecified amount of diesel from another tanker that sank at the mouth of Manila Bay, a coast guard statement said.

The vessel's owners had claimed the MTKR Jason Bradley was not carrying cargo, the statement said, but coast guard divers found leaks and sealed them.

The crew's whereabouts were unknown.

The 39-meter vessel sank in muddy waters about half a kilometer from the coast of Mariveles municipality. It did not say when the second tanker sank.

The sinkings occurred as heavy rains fuelled by Typhoon Gaemi and the seasonal monsoon lashed Manila and surrounding regions in recent days.

© Agence France-Presse

RELATED VIDEO: