Story highlights All 79 aboard transported off ship that struck Tubbataha Reef in the Sulu Sea, U.S. Navy says

Initial efforts to free the ship at high tide were unsuccessful

Tubbataha Reefs Natural Park is home to threatened and endangered marine species

The cause of the grounding was under investigation, Navy says

The U.S. Navy has evacuated all 79 crew members from a minesweeper that ran aground Thursday on a reef in the Philippines, the Navy's Seventh Fleet said in a statement Friday.

The 224-foot-long,1,312-ton ship was on its way from Subic Bay to its next port call when it struck the Tubbataha Reef, about 80 miles (130 kilometers) east-southeast of Palawan Island in the Sulu Sea, the Navy said.

Initial efforts to free the Avenger-class mine countermeasures ship at high tide were unsuccessful, and the crew was transferred by small boats to the USNS Bowditch and the MSV C-Champion, ships of the Military Sealift Command, according to the Navy statement.

"Seventh Fleet ships remain on scene and essential Guardian sailors will continue conducting survey operations onboard the ship as needed until she is recovered," Vice Adm. Scott Swift, U.S. Seventh Fleet commander, said in a statement. "Several support vessels have arrived and all steps are being taken to minimize environmental effects while ensuring the crew's continued safety."

Tubbataha Reefs Natural Park is a UNESCO World Heritage site and home to threatened and endangered marine species, including fish, corals and sharks.

"The site is an excellent example of a pristine coral reef with a spectacular 100-meter perpendicular wall, extensive lagoons and two coral islands," according to the UNESCO website.

The cause of the grounding was under investigation, the Navy said.

The Guardian is based in Sasebo, Japan.