QUILLON: Chilean authorities on Tuesday warned of a "very complex" situation as a new heat wave in the country's south-central region threatened to further fan the flames of dangerous forest fires that have already left 26 dead.

Over 290,000 hectares (716,606 acres) have been ravaged by fires this season, and forecasts for higher temperatures stretching from Santiago to the southern regions that have been the focal point of the flames have raised concerns about the 81 active fires.

Another 169 fires are under control.

High temperatures are forecast through Friday and could rise above 35 degrees Celsius (95°F) in the central Maule y Ñuble regions, "creating a very complex situation in terms of weather," Deputy Interior Minister Manuel Monsalve told reporters.

Monsalve said international fire brigades from Colombia and Mexico were arriving to offer assistance. He said 15 people had been arrested for possible links to starting the fires, several of them for activities such as welding or burning clothing and animal wool.

Air quality in the affected areas has deteriorated significantly due to the smoke from the fires, said Health Minister Ximena Aguilera.

Chile's massive pulp and paper company CMPC said in a statement on Tuesday that over 10,000 hectares (24,700 acres) of its plantations have been affected by the fires, while operations at some of its processing plants had been halted for security reasons.