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MANILA - Potentially dangerous mud flows or lahar could flow down the slopes of Mount Mayon in Bicol region as it continued to show signs of an impending eruption, the Philippine Institute of Volcanology and Seismology warned Tuesday.

Looming rains may mix with the ash and debris spewed by the volcano, resulting in lahar that can reach communities at the foot of the volcano, PHIVOLCS director Renato Solidum told ABS-CBN News.

• WATCH: Mayon Volcano spews lava fountain

A mud flow can grow to more than 10 times its initial size as it moves downslope. It can incorporate anything in its path, even buildings and bridges, according to the United States Geological Survey.

Occasionally heavy rains that can trigger lahar may hit Bicol on Tuesday due to the tail-end of a cold front, state weather bureau PAGASA said.

The chance of rain will increase if Mayon grows more restive and draws moisture from the air towards its eruption column, added Solidum.

Mayon has sprayed jets of lava into the air four times in the past 24 hours, PHIVOLCS said.

Pyroclastic flow -- which contains a high-density mix of hot lava blocks, pumice, ash and volcanic gas -- was also observed in the volcano on Tuesday morning.

WATCH: Pyroclastic flow event in Mayon Volcano caused by lava collapse | via @phivolcs_dost pic.twitter.com/xCXc9BsHOK

— ABS-CBN News (@ABSCBNNews) January 16, 2018

Mayon remains under alert level 3, which means a hazardous eruption is possible within weeks or days, Solidum said.

The highest alert, Level 5, indicates an eruption is in progress.

More than 12,000 people have been ordered to leave the 7-kilometer danger zone around Mayon's crater.

The volcano's most destructive eruption was in February 1814, when lava buried a town and killed 1,200 people. It last erupted in 2014, spewing lava and forcing thousands of people to evacuate. With a report from Reuters