MANILA, Philippines ? Widespread flooding caused by Tropical Storm ?Isang? (international codename: Molave) effectively shut down Metro Manila Friday, despite the center of the weather disturbance being hundreds of kilometers away in extreme northern Luzon.

President Gloria Macapagal-Arroyo declared a holiday early Friday morning in Metro Manila, later extending it to most of Luzon as flooded roads stopped traffic and caused vehicles to stall.

The announcement was made at 8 a.m. when most people were already at work. Pedestrians could be seen wading through knee-deep water early Friday morning.

Press Secretary Cerge Remonde said work, ?except for those in emergency, medical and security services? was being suspended because of the flooding and continued rains, on the recommendation of the Office of Civil Defense and the National Disaster Coordinating Council.

Packing maximum sustained winds of 95 kilometers an hour, Isang was headed for the sparsely populated Calayan islands in the Babuyan group off the coast of Cagayan in northern Luzon by early evening, the weather bureau said.

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pag-asa) said northern Luzon could expect up to 78.7 inches of rain within a 24-hour period, leading to potential flash floods and landslides.

The provinces of Aurora, Quirino, Nueva Vizcaya, Ifugao, Benguet, Mountain Province, Pangasinan, La Union and Ilocos Sur were placed under Signal No. 1 while Batanes, Cagayan, Isabela, Kalinga, Apayao, Abra and Ilocos Norte were under Signal No. 2.

Though no typhoon signal was raised in Metro Manila, classes were suspended Friday from preschool up to high school levels because of the nonstop downpour and strong winds since Thursday.

Makeup classes scheduled

Education Secretary Jesli Lapus sent text messages to reporters as early as 3:52 a.m. Friday and announced the class suspensions on radio at 4 a.m.

Education authorities said public school students should be prepared for a shorter semester break as makeup classes would have to be scheduled because of the class suspensions.

?It is important that our students complete at least 204 school days,? National Capital Region education director Teresita Domalanta said in a phone interview.

Private offices and the stock exchange also shut down. The Philippine Stock Exchange said it suspended operations mid-morning ?due to lack of clearing facilities? as the central bank had curtailed its activities because of the weather.

Many domestic flights were either grounded or delayed but authorities said the poor weather did not affect the scheduled international flights.

About 28 families in three small villages of Bicutan, Taguig City, were ordered evacuated as water rose to waist level.

Rising La Mesa Dam waters

The waters of La Mesa Dam rose past its 80.15-meter spillway and authorities said they were considering evacuating the surrounding neighborhoods.

Vehicles stalled on the stretch of the Southern Luzon Expressway from Filinvest Alabang to Sucat, Parañaque City, as authorities were forced to close a rush-hour counterflow lane.

Philippine National Police Director General Jesus Verzosa ordered all rescue-capable police units to be ready to be sent to disaster areas for relief, evacuation and rehabilitation operations.

The national police headquarters in Camp Crame said it received reports of flooding around Metro Manila and northern and Central Luzon.

In San Pablo City in Laguna, six barangays (villages) of Mabitac town were submerged and an undetermined hectarage of rice fields which were ready for harvest were flooded.

Monitor slide-prone areas

In Baguio City, heavy rains widened by 10 to 15 meters the openings that a June 5 landslide had made on the grounds of a high school in Mankayan town, Benguet province, the Cordillera OCD said.

The massive landslide at the mining town is a priority concern because the campus there is now part of a 10-hectare danger zone, the OCD said.

Geologist Benigno Espejo, who has studied Mankayan?s ground deterioration, said the slide had already weakened the soil and could immediately wash out due to the rains.

The OCD said families located near the danger zone had been evacuated.

Geologists also advised local governments to monitor several slide-prone areas in Ifugao and Kalinga provinces, which may not be able to withstand the strong rains.

Ifugao Gov. Teodoro Baguilat Jr. said rescue teams were on standby at Tinoc town, where a slide caused 1 million cubic meters of rock and soil to block the path of a river, raising threats of flooding in two villages.

Government work crews managed to punch through the slide, but the Mines and Geosciences Bureau last week declared the area a danger zone.

Except for minor slides that affected the Halsema Highway and several roads connecting Abra, Ifugao, Kalinga and Nueva Vizcaya, no major disruptions were reported in the Cordillera, the OCD said.

In Baguio City, strong rains also caused minor slides, but the city disaster coordinating council reported no injuries.

Heavy rains disrupted elementary and high school classes in the cities of Dagupan, Laoag, and Malolos, as well as in the Cagayan Valley provinces.

In Pangasinan province, residents of Rosales town braced for flooding in anticipation of the swelling of the Agno River, which passes through several towns.

Binga, Ambuklao dams

The Binga and Ambuklao dams in Benguet opened one spillway gate each at 1 meter and 1.5 meters, respectively.

As of Friday, Binga had a water level elevation of 573.35 meters, only 1.65 meters short from its flood season high water level of 575 meters.

The water level at Ambuklao was 744.69 meters, 7.31 meters away from its season high water level of 752 meters.

In Isabela, the water level at the Magat Dam had reached 190.1 meters but had not breached the 193-meter critical level.

In Bulacan, the rains were not strong enough to affect the water levels at Angat and Ipo dams.

Floods submerged low-lying towns of Obando and Hagonoy, but these were triggered by the swollen Manila Bay and not by storm rains. Reports from TJ Burgonio, Edson Tandoc Jr., Alcuin Papa, Tarra Quismundo, Beverly Natividad, Marlon Ramos and Niña Catherine Calleja in Manila; Romulo O. Ponte, Inquirer Southern Luzon; Cristina Arzadon, Vincent Cabreza, Yolanda Sotelo and Villamor Visaya Jr., Inquirer Northern Luzon; and Carmela Reyes, Inquirer Central Luzon