U.S. wargames chopper crashes in the Philippines

An army Chinook helicopter takes part in a deployment on Basilan island

WASHINGTON (CNN) -- A U.S. helicopter carrying eight crew members and two passengers has crashed over water in the southern Philippines, the Pentagon said.

A search-and-rescue effort is underway, but there were no immediate signs of survivors, the Pentagon said.

The MH-47 Chinook went down at 2:30 a.m. (1:30 p.m. EST) just off the coast of the south-central city of Dumaguete, about 150 km (93 miles) short of the islet of Mactan.

There was no indication the helicopter was brought down by hostile fire, the Pentagon and Philippine military officials said.

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The helicopter was flying in tandem with another U.S. Army Chinook when the plane crashed about 30 minutes before its scheduled arrival, according to U.S. and Philippine military officials who were meeting in Zamboanga about the crash.

The chopper was on a routine trip from the southern island of Basilan -- a stronghold of Muslim rebels -- to Mactan in the southern-central Philippines, where the United States has an air base, the Pentagon said.

About 160 U.S. Green Beret commandos flew to Basilan earlier this week to begin training Philippine troops to fight terrorism. Abu Sayyaf, a militant Muslim group U.S. officials have linked to the al Qaeda terror organization, is based on Basilan, about 560 miles south of Manila.

An advance party of around 25 U.S. troops had already arrived on the island to prepare the way for the U.S. Special Forces soldiers.

Around 500 other U.S. troops will be stationed in the cities of Zamboanga, on the western tip of Mindanao island, and Cebu, which is near that island's center, officials say. About 200 U.S. soldiers are based at Mactan, mainly for air logistics support.

Despite their role as trainers, the American forces are prepared for action and casualties, said Robert Fitts, charge d'affaires for the U.S. Embassy in Manila.

"There is the possibility of hostile contact, but I would personally rate that as a possibility and not a probability," Fitts said.

Philippine officials and civilians have debated the role and capability of U.S. forces in the six-month "war games," which some have called the most significant expansion of the U.S.-led war on terror since the beginning of the Afghanistan campaign in October.

The Abu Sayyaf has kidnapped scores of hostages in the past two years and has beheaded more than a dozen, including American tourist Guillermo Sobero.

The group claims to be fighting for an independent Islamic state in the southern Philippines but has been dismissed by the Philippine government as no more than a kidnap-for-ransom gang.

The U.S. government considers the Abu Sayyaf a target in its global campaign against terrorism.