Philippine President Benigno Aquino welcomed the US Navy’s apology after a minesweeper ran aground on a World Heritage-listed coral reef, but said Washington would not be exempt from penalties for the damages.

The Philippine government is seeking heavy fines for the coral damage which would have to be assessed after the ship is salvaged, AP reports.

“We’d like to thank them for respecting our sovereignty and are very careful about our sensitivities,” Aquino told reporters in Davos, Switzerland, speaking of the apology from the US embassy and US Navy.

“But that doesn’t exempt them from having to comply with our laws,” he said. “They violated it, there are penalties”.

An investigation was under way on why the 68-meter (224-foot) USS Guardian strayed into the area, where it has been stuck since January 17 on the Tubbataha Reef.

Under the Philippine law, the sanctuary off Palawan Island in the Sulu Sea is off-limits to ships except for research or tourism vessels approved by the government.

The head of the marine park supervising the Tubbataha has said the ship ignored warnings that it was entering a protected marine sanctuary, Both the US embassy and the head of the US Navy’s Pacific fleet have not yet explained the exact cause.

The US Navy last week raced to remove some 57,000 liters (15,000 US gallons) of fuel from the battered ship as water flooded the punctured hull. The ship is too damaged to be towed away and will have to be lifted to another ship, the US Navy said.

About 1,000 square meters (3,280 square feet) of coral has been impacted, or about less than one percent of the entire marine park.