Investigators comb the debris of an upmarket apartment building in Manila, looking for the cause of an explosion that left three people dead.<br/> <br />The powerful blast in Fort Bonifacio complex ripped a wall off a condominium unit and sent debris flying onto the street, crushing a driver and two delivery men.<br/> <br />Five others were injured and residents from 35 flats were evacuated from the building.<br/> <br />Gas and electricity lines were shut down.<br/> <br />Investigators say it may take several days to determine the cause, though Interior Secretary Manuel Roxas said sniffer dogs hadn't detected explosives.<br/> <br />(SOUNDBITE) (English/Filipino) INTERIOR SECRETARY MANUEL ROXAS SAYING:<br/> <br />" We still can't find what caused the explosion. All forensic evidence was checked by the bureau of fire protection and the police."<br/> <br />Burn traces in two units damaged by the blast also showed no evidence of explosives.<br/> <br />The occupant of the apartment where the blast occurred suffered burns but is i
