A heatwave is threatening further wildfires in Chile’s south-central region, authorities have warned, as more than two dozen people have been killed due to the devastating blazes.

High temperatures are expected until Friday and could rise above 35 degrees Celsius (95 degrees Fahrenheit) in the central Maule and Nuble regions, “creating a very complex situation in terms of weather”, the deputy interior minister, Manuel Monsalve, said on Tuesday.

“A very complex climate situation can arise,” said Monsalve, urging teams to be “prepared for any eventuality”.

Fires have ravaged more than 290,000 hectares (716,606 acres) across the South American nation so far, killing at least 26 people and destroying more than 1,000 houses, leaving thousands homeless.

Approximately 5,600 firefighters, mostly volunteers, are actively battling 81 priority blazes countrywide out of 301 still burning, the AFP news agency reported, citing Chilean authorities.

Air quality in the affected areas also has deteriorated significantly because of the smoke from the fires, said health minister Ximena Aguilera.

Nearly 2,000 people have been injured in a week of blazes in the regions of Biobio, La Araucania and Nuble, where a state of emergency has been in place.

Monsalve, the deputy interior minister, said on Tuesday that fire brigades from Colombia and Mexico were arriving to help. He added that 15 people had been arrested for possible links to starting the fires over activities including welding and burning animal wool.

Meanwhile, Colombian President Gustavo Petro said on Twitter that his country was sending a firefighting brigade and cargo plane with two Bambi Buckets – used to help extinguish blazes from the air – to Chile.

Spain, Mexico and other countries in Latin America also have said they would send firefighters and experts to help combat the fires.

One of the local volunteers, Macarena Fernandez, a 31-year-old physical education teacher, described the situation in Chile’s Santa Juana region late last week as “intense”.

“We did what we humanly could, what was within our means,” she told AFP.

“The most difficult is to see the situation of people left without homes, without their family, without their animals and completely destitute.”

But a week into the emergency, the government said some employers were calling on volunteers to return to their normal jobs.

“The more days [of fire], the more we need the volunteers, the more tired they are and the more in need of help,” said interior minister Carolina Toha.

Earlier this week, Chile’s President Gabriel Boric called for unity and resolve in response to the destruction left by the fires.

“Unity to face the tragedy, unity to rebuild ourselves. That has been and will always be the path in the face of adversity in our Chile,” he wrote on Twitter on Monday.

Officials in Chile have previously suggested that climate change was to blame for the rising temperatures and subsequent fires.

Scientists have been warning that the climate crisis – fuelled by human activity, namely the emission of greenhouse gases – will lead to increased risks of natural disasters, including wildfires, droughts and hurricanes.

“The evolution of climate change shows us again and again that this has a centrality and a capacity to cause an impact that we have to internalise much more,” Toha, the interior minister, said earlier this month.

“Chile is one of the countries with the highest vulnerability to climate change and this isn’t theory but rather practical experience.”