Authorities in the Philippines have lowered the alert level around Mount Mayon, a volcano which spewed ash and lava for several weeks.

Thousands of local residents, who were forcibly evacuated from their houses near the volcano on the main island of Luzon, were preparing to return home on Saturday.

Scientists had warned of the possibility of a dangerous eruption, and on December 20 - as activity inside the volcano intensified - the alert level was raised to four on a five-point scale.

Nearly 50,000 people were evacuated from the area and during Christmas holidays, government troops had been ordered to enforce an extended 10km no-go zone.

Most will now be allowed to return home but a six-kilometre danger zone remains in force around the volcano, meaning around 3,000 people will have to remain in evacuation camps.

Despite the volcano appearing to have settled into a more moderate eruption phase, Renato Solidum, the director of the Philippine Institute of Volcanology and Seismology, says danger still remains around Mount Mayon.

"The situation could change and we could raise the alert level again. This is what happened in 2001 when Mayon paused for a long time and then resumed erupting," Solidum said.

Mayon is the most active of 22 volcanoes dotted across the Philippines. In the latest eruption, lava flowed from the dome of the 2,460-metre Mayon for more than two weeks, with clouds of ash ejected up to 2km into the sky.

Located about 330km southeast of Manila, the Philippines capital, Mayon has erupted 48 times in recorded history.