State seismologists on Tuesday maintained that the four-kilometer radius Permanent Danger Zone (PDZ) must be off-limits from the public saying 'sudden and more explosive eruption' is still possible over Kanlaon Volcano in Negros Island.

The Philippine authorities ordered nearly 90,000 people to evacuate after a volcano on the central island of Negros erupted, spewing a two-mile-high plume of deadly ash, lava and large rocks. The volcano,