(UPDATED) - THE Philippine Institute of Volcanology and Seismology (Phivolcs) has recorded over 400 aftershocks following the magnitude 6.1 tectonic earthquake that struck parts of Luzon Monday, April 22, and killed seven people.

The agency said 470 aftershocks were recorded as of 12 noon Tuesday, April 23, after the tremor plotted at 18 kilometers northeast of Castillejos, Zambales. It had a depth of focus of only 10 kilometers.

Of the total, eight were felt particularly in the provinces of Pampanga and Zambales, 66 were plotted which means its epicenters were identified, and the rest were too weak either to be felt or plotted.

Phivolcs said these aftershocks were as strong as magnitude 3.4 and as weak as magnitude 1.4. Aftershocks as strong as magnitude 5 may be experienced throughout the week, the agency said.

Pampanga, which sustained the biggest damage to lives and property, was also jolted by a series of minor earthquakes.

As of 5:37 a.m. Tuesday, more than 20 minor quakes with magnitude of up to 3.5 were recorded near Angeles City, Pampanga based on the Phivolcs list of earthquake bulletins.

Four tremors with magnitude 1.5 to 2.7 were recorded near Porac town, Pampanga from 11:55 p.m. of April 22 to 5:15 a.m. of April 23 while two quakes with magnitude 1.4 and 2.7 centered near Floridablanca in Pampanga were tapped as of 9:41 p.m. Monday.

John Paul Fallarme, Phivolcs research assistant, said they were still investigating which fault moved to cause the earthquake.

Initially, he said the quakes that struck Zambales and Pampanga were connected. A magnitude 4.1 earthquake plotted near Lubang, also on Monday, was caused by movement in the Lubang faultline in Batangas.

Four people have been confirmed dead in Porac, Pampanga, where a building housing the Chuzon Supermarket collapsed.

Edgar Posadas, National Disaster Risk Reduction and Management Council (NDRRMC) spokesperson, said seven people were killed, 81 were injured and 24 remained missing as of Tuesday morning.

He said search, rescue and retrieval operations is still ongoing at the Chuzon Supermarket.

Posadas said 32 structures were affected by the tremor in the National Capital Region (NCR) and Central Luzon.

The quake also caused part of the Porac Church to crumble and part of the ceiling of the Clark International Airport passenger terminal to cave in.

Airport operations have been suspended while more than 40 flights to and from Clark have been cancelled.

Public Works Secretary Mark Villar said the Megadike Access Road was closed to traffic from Dolores to Calibutbut/Maliwalo in Bacolor, Pampanga.

The Floridablanca Consuelo Bridge, also in Pampanga, was also shut down temporarily due to road cracks.

At the Sasmuan-Lubao Bridge, still in Pampanga, only light vehicles were allowed to pass as of Tuesday morning.

Villar said the Dinalupihan-Pampanga boundary arch also collapsed due to the earthquake.

In Manila, the Emilio Aguinaldo College now leans against an adjacent building.

Work in government offices and classes were cancelled for Tuesday to allow authorities to check the integrity of the buildings. (SunStar Philippines)