At least 10 people were injured in an explosion Thursday outside an airforce base in the southern Philippine city of Zamboanga, media reports said.Civilians were mainly injured in the blast just outside of the Edwin Andrews Airforce base, according to a report on the GMA 7 television web site."We are still trying to determine the extent of the explosion," Zamboanga City acting police chief Lurimer Detran told dzBB radio.He gave no further details and declined to comment on whether the explosion was an accident or a bomb.