Canary Islands regional president Fernando Clavijo said police suspected arson and had opened three lines of investigation, but did not reveal whether there had been any arrests.
Tourists on the Spanish island are among those who have been affected by the impact of the fire.
‘Very difficult night’
Hundreds of soldiers and firefighters have been deployed to get the flames under control, and improved weather conditions helped them make more progress on Sunday.
Governor Rosa Davila said after a “very difficult night”, emergency services had enjoyed some “positive results”.
Many locals are sheltering in sports halls, clubs, and pavilions and no injuries have been reported.
People are being urged to stay inside due to the poor air quality, and to wear masks if they must venture outdoors.
Despite the apocalyptic scenes, Ms Davila said no homes had been lost yet, but 29,000 acres of pine forest and scrubland have been burned, and mountainous terrain around some towns is proving challenging for firefighters.
Water-carrying helicopters and planes are assisting with the response, which has not been helped by the fact the Canary Islands have been in drought for much of the past few years.
There has been below-average rainfall because of changing weather patterns caused by climate change.
Meanwhile, Spain‘s mainland is expected to endure heatwave temperatures for the next several days, with temperatures topping 40C (104F) on Wednesday and Thursday.