The massive blazes in recent days have killed at least 21 people and affected some 20,000 others, according to the government.

Firefighters were on Thursday battling 19 fires still burning in the hardest-hit regions of Araucania, Nuble, and Biobio.

A man was arrested in the early hours of Thursday as he was lighting a fire in a forested area of Punta de Parra, a town of about 3,000 residents surrounded by eucalyptus forests, police said.

Two other people were arrested earlier in the week: one in Biobio Monday, who was released shortly thereafter, and the other in Araucania on Wednesday.

"It's pure malice, just to cause harm -- there's no other explanation," Felicia Lara, a 68-year-old resident of Punta de Parra, told AFP. Her house was one of those destroyed by a wildfire that wiped out much of the town.

High temperatures amid the Southern Hemisphere summer and strong winds have fueled the spread of the flames.

Wildfires have severely impacted south-central Chile in recent years, especially in its warmest and driest months of January and February.

A 2024 study led by researchers at the Santiago-based Center for Climate and Resilience Research, found climate change had "conditioned the occurrence of extreme fire seasons in south-central Chile" by contributing to a long-term drying and warming trend.

In February 2024, several fires broke out simultaneously near the city of Vina del Mar, northwest of Santiago, resulting in 138 deaths, according to the public prosecutor's office.

Investigations later found some of those blazes had also been deliberately started.