Manila, Aug. 29 -- The Philippine Institute of Volcanology and Seismology (Phivolcs) on Saturday warned of lahar flows from Pinatubo and Taal volcanoes amid heavy rains brought by the southwest monsoon.

In an advisory, Phivolcs said heavy rains could generate volcanic sediment flows or lahars, muddy streamflows or muddy run-off in rivers and drainage areas.

"Prolonged and intense rainfall may generate non-eruption lahars on major rivers draining western Pinatubo Volcano where significant deposits of the 1991 pyroclastic density currents (PDCs) remain on the watershed," it said.

According to Phivolcs, Pinatubo lahar flows are likely to be channel-confined and occur on the upper to middle reaches of the Sto. Tomas- Marella and Bucao Rive...