Blasts at a suburban Manila police ammunition dump injured at least 107 people, damaged several buildings and homes. Police ruled out sabotage or terrorism.
Late Monday's explosions, which investigators say were apparently touched off by lightning, initially raised concerns of foul play due to swirling coup rumors linked to the monthslong political crisis hounding President Gloria Macapagal Arroyo.
She has been accused of rigging last year's election but has denies the allegations.
An ammunition bunker filled with World War II vintage bombs and homemade explosives seized from Muslim militants and fishermen was obliterated by the explosions, which also damaged nearby buildings and homes in and out of Camp Bagong Diwa.
The blasts shattered glass windows and ripped off parts of the roof of a dormitory for drug addicts at a rehabilitation center, hurled about 30 parked vehicles away and damaged a gas station, witnesses said.
The injured included 101 patients at the drug rehabilitation clinic, four elite police officers and two civilians, police said.
Residents living in and out of the camp recalled hearing small explosions followed by two large ones that rained debris on their roofs, shattered glass windows and knocked down wall pictures and flower vases, driving many of them out into a thunderstorm.
Police Supt. Warlito Tubon, explosives and ordnance disposal chief, said the destroyed munitions bunker had contained 30 50-kilogram bags of ammonium nitrate, 420 mines, some C-4 explosives plus anti-tank ammunition.
He ruled out terrorism or sabotage based on accounts of witnesses who said a series of small and large explosions followed a blackout during a thunderstorm. Police pointed to a blackened lightning rod they said showed that lightning struck the armory.
SWAT teams immediately tightened security at the camp, where suspected rebels from the al-Qaida linked Muslim extremist group Abu Sayyaf are detained in a maximum-security jail.
Interior Secretary Angelo Reyes said an investigation was underway, the AP reports.