MANILA - The Philippine Institute of Volcanology and Seismology (Phivolcs) on Thursday raised Taal Volcano's status to alert level 1 and said it was at an "abnormal condition."

In an advisory, Phivolcs reminded the public that the volcano's main crater remained "strictly off-limits because sudden steam explosions can occur and high concentrations of lethal volcanic gases can be released."

It added that the entire volcano island is a "permanent danger zone (PDZ), and permanent settlement in the island is strongly not recommended."

"The northern portion of the Main Crater rim, in the vicinity of Daang Kastila Trail, can also become hazardous when fumarolic or degassing activity along existing fissures suddenly increases," it said.

The agency said it raised the alert level after having recorded 50 volcanic earthquakes in the area since March 22.

"This recent earthquake swarm may indicate rock-fracturing beneath the edifice possibly associated with hydrothermal activity," it said.

Phivolcs also noted the changes in ground deformation, where there was slight inflation in the volcanic edifice starting January this year.

There was also a slight increase in the input of volcanic carbon dioxide from the hydrothermal system into the lake, Phivolcs said.

Phivolcs said alert level 2 may be raised if it recorded 100 volcanic earthquakes. Alert level 1 was last raised in 2013.

--With a report from Arra Perez, ABS-CBN News