MANILA, Philippines >> Most of the sailors on a U.S. Navy minesweeper that struck a coral reef in the Philippines left the ship today for safety reasons after initial efforts to free the vessel failed, the Navy said.

The ship ran aground Thursday while in transit through the Tubbataha National Marine Park, a coral sanctuary in the Sulu Sea, 400 miles southwest of Manila. There were no injuries or oil leaks, and Philippine authorities were trying to evaluate damage to the protected coral reef, designated by UNESCO as a World Heritage Site.

The U.S. Navy’s 7th Fleet said 72 of the 79 crew of the USS Guardian were transferred to a military support vessel by small boat. A small team of personnel will remain aboard and attempt to free the ship with minimal environmental impact, the statement said. The remaining seven sailors, including the commanding and the executive officer, will also be transferred if conditions become unsafe.

Philippine officials said the weather was choppy Friday with strong winds and rough seas.

The World Wide Fund for Nature Philippines said that according to an initial visual inspection, the 68-meter- (74-yard-) long, 1,300-ton Guardian damaged at least 10 meters (yards) of the reef. Aerial photographs provided by the Philippine military showed the ship’s bow sitting atop corals in shallow turquoise waters. The stern was floating in the deep blue waters. The Navy said the cause of the grounding, which took place around 2 a.m. Thursday, was under investigation.

Angelique Songco, head of the government’s Protected Area Management Board, said it was unclear how much of the reef was damaged. She said the government imposes a fine of about $300 per square meter (yard) of damaged coral.

In 2005, the environmental group Greenpeace was fined almost $7,000 after its flagship struck a reef in the same area.

Songco said that park rangers were not allowed to board the ship for inspection and were told to contact the U.S. Embassy in Manila. Their radio calls to the ship were ignored, she said. The U.S. Navy statement said that “the government of the Philippines was promptly informed of the incident and is being updated regularly.”

Philippine military spokesman Maj. Oliver Banaria said the U.S. Navy did not request assistance from the Philippines.

U.S. Navy ships have stepped up visits to Philippine ports for refueling, rest and recreation, plus joint military exercises as a result of a redeployment of U.S. forces in the Asia-Pacific region.

The Philippines, a U.S. defense treaty ally, has been entangled in a territorial dispute with China in the South China Sea.

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Associated Press writer Oliver Teves contributed to this report.