MANILA — The Philippine Coast Guard has collected some 9,000 liters of oily water mixture in Oriental Mindoro, where a leaking tanker went down in rough seas a month ago.

The PCG on Monday said it collected 9,463 liters of oily water mixture and 115 sacks of contaminated materials in its offshore operations to contain spillage from the sunken Princess Empress.

In its shoreline response, the PCG said it also collected 3,514.5 sacks and 22 drums of waste collected from 13 affected barangays.

The Princess Empress was carrying 800,000 liters of industrial fuel oil when it sank on February 28 off Mindoro, known for its rich marine life.

Five out of 8 tanks in the vessel "suffered structural damage." The damaged tanks contained around 400,000 liters of cargo, PCG Deputy Commandant for Operations Vice Admiral Rolando Lizor Punzalan Jr. said on Tuesday.

"Ito ay maaari nating sabihin sa kasalukuyan, not very accurate though, ito na yung na-release during the first week, kung kaya’t nakita natin iyong area na na-cover ng spill," he told ABS-CBN's TeleRadyoo.

"Ang natitira natin ay lalabas ‘yang less than 350,000 [liters] or so dahil ang presumption po natin, dahil may leakages na nakita, mas maliit na po dito sa amount na ito which was reported to be in the tanks that did not suffer structural damage."

(We could say, although not very accurately, that this was what was released during the first week. We're left with less than 350,000 liters or so because our presumption is, due to the leakages, this would be less than the amount which was reported to be in the tanks that did not suffer structural damage.)

The cleanup has entered its second phase, where authorities would use specialized bags to contain the seepage and later siphon off the oil, said the official, who could not give a timeline for the operation's completion, pending feedback from other experts.

Diesel fuel and thick oil from the vessel have contaminated the waters and beaches of Oriental Mindoro province and other islands.

The tanker was found by a Japanese remotely operated underwater vehicle (ROV) nearly 400 meters below the waves, authorities said last week.

The Philippines has sought assistance from several countries, including Japan, the United States and France, to help contain and clean up the slick.

Thousands of hectares of coral reefs, mangroves and seaweed could be affected, officials have said.

Oil spill booms made out of hay, human hair and other materials have been deployed to try to protect coastal waters that people in the fishing and tourism industries rely on for their livelihoods.

Oil has been spotted as far away as Casian Island, off the north coast of the western island of Palawan, about 350 kilometers southwest of where the tanker sank.

As feared, oil has also drifted north to the Verde Island Passage -- a busy sea lane between Mindoro and the Philippines' main island of Luzon.

Environment Secretary Maria Antonia Loyzaga said previously that the area was "globally recognized" for its marine biodiversity.

Tens of thousands of people have been affected by the spill, with scores falling ill. The government is distributing food packs and other assistance.

Among the hardest hit are fishermen, who have been ordered to stay on shore until they can fish safely.

— With a report from Agence France-Presse