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MANILA - The Mayon Volcano spewed a fountain of lava and an ash plume for the third time Tuesday afternoon, hours after a similar event as authorities and residents remained on alert for a hazardous eruption.

• Rumbling Mayon spews more ash after lava flows

Phivolcs Director Renato Solidum said the explosion was a "strombolian eruption" where lava "fountaining" or an ejection of lava could be seen.

"Strombolian eruption [is] where you can actually see fireworks or lava fountaining with lava flow and you can also see an ash plume of around 3 kilometers. In daytime, you would not be able to see that, just the ash plume," Solidum told ANC.

Lava has also flowed from different directions from the volcano's crater.

"Essentially, the start of the eruption, the crater lid of the Mayon Volcano was opened or lowered to the southern part. The lava flow was preferential simply because the lava flow activity was not accompanied by a strombolian activity," Solidum said.

"But since the other night when the strombolian eruption started, it is explosive but not as explosive for the other types of eruption of Mayon, then the lava can be scattered all over. Essentially, the vertical column would explode, then the lava would drop and flow down to all directions."

The volcano started spewing lava and ash plumes on Monday.

At least 40,000 residents have been evacuated in nearby towns after the second highest alert in a five-step warning system was raised over Mayon on Monday, which means hazardous eruption is imminent.

Solidum said Alert Level 5 would be raised if there is continuous eruption.

"Alert level 5 is essentially just a statement that a hazardous explosive eruption is ongoing and this must be sustained. Not like what we’re seeing now, when explosion would occur and stop, so we need to see tall eruption columns with sustained eruptions and these can produce ashes and rocks falling down the slope," he said.

Local authorities are preparing for possible preemptive evacuation in towns in the outskirts of the 8-kilometer danger zone in preparation for a possible big explosion. -- With a report from Jose Carretero, ABS-CBN News