The commanding officer and three crew of a US minesweeper which ran aground on a protected coral reef in the Philippines have been relieved of their duties, the US Navy said Thursday.

A statement from the US Pacific Fleet in Hawaii said an initial investigation had found that the commander of the USS Guardian and three others had failed to “adhere to standard US Navy navigation procedures.”

“The US Navy has the highest accountability standards and all four sailors were relieved by Rear Admiral Jeffrey Harley due to their role in the grounding and a loss of confidence,” a statement said.

The minesweeper ran aground on Tubbataha in a remote part of the Sulu Sea on January 17, damaging a section of the reef, a UNESCO World Heritage site known for its rich marine life.