MANILA, May 20 (Xinhua) -- Two people were killed and two others injured in a fire that broke out in a crowded residential area in the Philippine capital, the Bureau of Fire Protection said Tuesday. 

The bureau said the three-hour blaze, which occurred on Monday afternoon, quickly spread in the closely packed houses made of light materials. 

Officials said the two killed, who were cousins, were trapped inside their house. 

The fire damaged a nearby school building and torched several vehicles. 

Residents told firefighters that they had heard a loud explosion and saw smoke billowing from one of the houses before the fire. 

Local authorities said the cause of the fire is under investigation.