(UPDATE) A magnitude 5.7 earthquake struck Luzon Monday afternoon, forcing people to flee from buildings in Metro Manila and nearby areas.
The tremor struck near Castillejos, Zambales at a depth of 21 kilometers, Phivolcs said.
The earthquake could have originated from either the Manila Trench or a faultline in Zambales, Phivolcs Undersecretary Renato Solidum told dzMM Teleradyo.
The quake was felt at intensity 5 in Zambales and Quezon City in Metro Manila.
The tremor is expected to cause damage and trigger aftershocks.