The Philippines' most active volcano oozed lava and shot up plumes of ash Tuesday, forcing thousands of people to evacuate their homes and face the possibility of a bleak Christmas in a shelter.

State volcanologists raised the alert level on the cone-shaped, 8,070-foot (2,460-meter) Mayon volcano overnight to two steps below a major eruption after ash explosions.

Dark orange lava fragments glowed in the dark as they trickled down the mountain slope overnight. Renato Solidum, head of the Philippine Institute of Volcanology and Seismology, said the activity could get worse in coming days.

"It's already erupting," Solidum told The Associated Press.

More than 20,000 people were evacuated to safety by nightfall Tuesday, said Gov. Joey Salceda of Albay province, where Mayon is located about 210 miles (340 kilometers) southeast of Manila.

The first of 20 vehicles, including army trucks, were sent to villages to take residents to schools and other temporary housing, provincial emergency management official Jukes Nunez said.

"It's 10 days before Christmas. Most likely people will be in evacuation centers, and if Mayon's activity won't ease down we will not allow them to return to their homes," Nunez said. "It's difficult and sad, especially for children."

Residents in Albay are used to moving away from Mayon. Nearly 50,000 people live in a five-mile (eight-kilometer) radius around the mountain, and some villages were evacuated last month when the volcano spewed ash.

Mayon last erupted in 2006, and about 30,000 people were moved. Another eruption in 1993 killed 79 people.

Salceda said Tuesday that he has placed the central province under a "state of imminent disaster," which will make it easier for him to draw and use emergency funds.

Although the alarm has been sounded, life continued normally in many laid-back farming villages near the restive volcano. Throngs of farmers flocked to the town hall in Guinobatan, which lies near the danger zone, for a Christmas party, then headed home bearing gifts.

Village leader Romeo Opiana said the 249 residents in his farming community of Maninila, near the volcano, readied packs of clothes but no one had left. An army truck was parked nearby, ready to haul people if the threat grows.

"We're ready, but we're not really alarmed," said Opiana, 66. He could not remember how many times he had seen Mayon's eruptions since childhood.

Provincial governor Salceda said he had decided to cancel a trip to Copenhagen, where he was to attend the U.N. climate conference to discuss his province's experience with typhoons and other natural disasters.