La Mesa Dam, the reservoir for Metro Manila, overflowed on Friday morning and threatens residents near Tullahan River in Quezon City.
Jeric Sevilla, spokesman for Manila Water, said the dam reached its spill level of 80.15 meters at 10:10 a.m. Friday.
Sevilla told DZMM radio the dam level reached 80.17 meters.
He said Manila Water was coordinating Quezon City authorities in moving out the residents, most of them illegal settlers, and bringing them to an evacuation center in Fairview.
Large sections of Metro Manila were flooded on Friday as Storm Mario and the habagat rains brought rains to the metropolis and nearby provinces.
Malacanang suspended classes in all levels in Metro Manila and nearby areas.
Areas where classes are suspended are Metro Manila, Zambales, Bataan, Pampanga, Tarlac, Nueva Ecija, Bulacan, Rizal, Cavite, Batangas, Laguna, Quezon, including Polillo Island, Mindoro Provinces, Camarines Norte, Marinduque and Pangasinan.
CATHERINE VALENTE and radio reports