In a statement released on Sunday afternoon, police said a 55-year-old man was detained on suspicion of starting a blaze in the Portuguese district of Castelo Branco, where the wildfires started on Saturday (July 20) before spreading to nearby Santarem.
Internal administration minister Eduardo Cabrita said police had opened an investigation into the fires.
Strong winds and high temperatures were making it harder for firefighters to put out the remaining wildfire, although they have been able to control 85% of the flames in Vila de Rei, a municipality in Castelo Branco, 225 kilometers (139 miles) northeast of the capital Lisbon.
Thirteen airplanes and 243 firefighting vehicles on the ground are battling the blazes, along with 20 soldiers and four bulldozers.
Twelve civilians and eight firefighters were injured in Saturday’s fires, Cabrita said. One is in a serious condition and remains hospitalised with first and second degree burns.
Castelo Branco remains under a yellow risk alert with temperatures expected to reach 31 degrees Celsius on Sunday, according to the national meteorological agency.
In June 2017, a devastating wildfire in the central town of Pedrogao Grande killed 64 people and injured more than 250. The fire was the worst disaster in modern Portuguese history.