A small volcano in the Philippines erupted violently on Sunday, triggering waves of earthquakes, blanketing the area in a layer of ash, and forcing tens of thousands of residents to flee their homes. Authorities have warned that the eruption could worsen, endangering the lives of the residents who returned to their homes after the initial blast.

The Taal volcano, one of the region’s most active, fired debris and steam miles in the air Sunday and released a plume of ash into the sky, while lava gushed freely into the surrounding lake water early Monday. Clouds of ash drifted more than 60 miles north of the volcano, reaching the capital of Manila 40 miles from the island where the small volcano is located. There have been no reported fatalities, according to the Associated Press.

More than 30,000 people have fled their homes so far, according to the AP. Experts warned residents of lakeshore communities to evacuate, as the seismic activity—dozens of earthquakes have been reported—placed them in danger of tsunamis.
Many people reportedly returned to their homes near the volcano in defiance of evacuation orders once the ash from the initial blast had settled. Some told reporters that they were concerned about their livestock and worried about their livelihoods.

But experts have said that a major and more dangerous eruption is still possible, and on Sunday officials warned the volcano could escalate to a “Level 5” incident—the highest on the scale—within days. Authorities said they were preparing for the possible evacuation of hundreds of thousands of people, according to the AP.
The country’s main airport was also shut down on Sunday, canceling more than 500 flights, but it partially reopened on Monday after the ash fall relented.

The volcano last erupted in 1977. In a 1965 eruption, more than 200 people were killed. The island it occupies has been declared a “permanent danger zone,” and all residents of villages on the island itself have been safely evacuated. It’s not clear how long the activity in the volcano will continue.