Families living at the foot of Mount Bulusan volcano in Sorsogon were forced to leave their homes Wednesday night when heavy downpour loosened more volcanic deposits, triggering lahar that swelled the river channels in four villages in Irosin town, officials said.

Irosin Mayor Lilia Gonzales said a total of 276 families, or 1,596 people, evacuated as heavy rains mobilized more volcanic deposits and boulders that found their way to gullies and river channels in the barangays of Monbon, Cogon, Mapaso and Patag, even destroying a bridge in Monbon.

Gonzales said the evacuees took temporary refuge in five evacuation centers put up at the Irosin town proper. She said they have sought the help of government agencies to provide the evacuees with relief goods and to desilt the river channels of volcanic debris.

"The threat is real. There is an urgent need to immediately remove these volcanic materials from the river channels before another event of heavy rains loosen more debris that are now redirected to the residential areas," Gonzales said in a radio interview.

President Arroyo, meanwhile, ordered the government agencies concerned to provide assistance to the mudflow victims.

Social Welfare and Development Secretary Esperanza Cabral told reporters that her department has sent relief goods, including rice, canned goods and clothing, to Irosin town.

Raffy Alejandro, Bicol director of the Office of Civil Defense, said the mudflows have half-buried at least 10 houses in Monbon. He said his office has alerted other members of the Regional Disaster Coordinating Council to avert any untoward incidents should the condition around Bulusan worsen.

Alejandro said volcanic deposits washed out by the heavy downpour are now slowly creeping toward residential areas.