Philippine blast 'suicide attack'
ZAMBOANGA, Philippines (CNN) -- Investigators in the Philippines believe rebels may be responsible for a bomb blast at a military base that killed two Filipinos and a U.S. soldier.
The United States has condemned the bomb attack in which more than 20 people were wounded, including a second U.S. serviceman.
U.S. and Filipino investigators swarmed over the devastated site Thursday, looking into the possibility of a suicide attack. Officials said they were also trying to determine if the explosive had detonated prematurely.
The explosion occurred Wednesday outside a restaurant frequented by American and Filipino soldiers near Malagutay, a small military base on the southern Philippine island of Zamboanga.
Pentagon officials said the bomb was believed to be strapped to a motorcycle. No claims of responsibility have come in, officials said. The Filipino driver of the motorcycle, who was killed, was suspected of carrying the bomb.
The soldiers were part of a group of U.S. Special Operations unit conducting counter-terrorism exercises with the Philippine military and humanitarian aid workers.
Pentagon officials did not yet have word on any specific assignment or other explanation as to the activities of the U.S. soldiers in that area at the time of the blast.
Search is on
Philippines Brig. Gen. Eduardo Purificacion said investigators were searching houses and interviewing possible witnesses.
"We do not know where the bomb was supposed to be brought," said Purificacion.
"The driver of the motorcyle loaded with the bomb stopped and was checking something in his motorcycle when the bomb exploded."
Defense Secretary Angelo Reyes said the bombing also could have been the result of a grudge against a local the owner of a local restaurant. Asked about the possibility of a suicide attack, he said: "It might be too early to say. We are still investigating."
The explosion happened about two miles west of Camp Navarro, home to most of the U.S. troops in the area.
Security has been tightened in the area ahead of an October 12 Christian festival in the middle of the southern islands that make up the archipelago's Muslim heartland.
Amid worries of further attacks, more troops were being sent in, and checkpoints were set up on major roads and outside the city's power plant.
About 1,300 U.S. troops arrived in the Philippines in February to help root out terrorist elements in the southern region of the country.
The operation focused on Abu Sayyaf, a Muslim rebel group. Both the U.S. and Philippine governments say Abu Sayyaf has ties to Osama bin Laden's al Qaeda terror network.
Most of the U.S. troops left in August, after concluding a joint anti-terrorism training drill with the Philippine military.
-- CNN Pentagon Producer Mike Mount contributed to this report