A firefighter and a forestry official have been arrested on suspicion of starting a fire that killed 137 people in Vina del Mar city.

“An arrest warrant was issued today against the person who started the fires in February in the Valparaiso region,” where Vina del Mar is located, police director Eduardo Cerna told a news conference.

A little later, the Valparaiso regional prosecutor’s office confirmed the arrest of a second suspect, an official of the National Forestry Corporation (Conaf), the body responsible for fighting forest fires and managing national parks.

Both men will be remanded in custody on Saturday on charges of arson resulting in deaths.

Several fires broke out simultaneously on February 2 around the coastal city of Vina del Mar, 70 miles (110km) northwest of Chile’s capital Santiago.

The inferno, the second deadliest in the world this century, was fuelled by winds and a heatwave that saw temperatures of about 40 degrees Celsius (104 degrees Fahrenheit).

Local media reported the firefighter is a 22-year-old man who joined the volunteer force a year and a half ago.

“We are completely devastated by what happened, it is a totally isolated incident … we have served Valparaiso for more than 170 years and cannot allow such things,” Vicente Maggiolo, commander of the 13th Fire Company of the city of Valparaiso, told reporters.

‘An intentional attack’

Ivan Navarro, chief of the environmental crime investigation authority, said detectives reconstructed what the arrested firefighter did before, during and after the fire.

“We were able to determine the exact locations where the fires broke out and find the device that started them,” he said. “We were also able to determine the involvement of a second person, accused of being the mastermind behind the arson.

“He provided him with the knowledge to make these devices and also told him the exact times he needed to operate so that the fire would do more damage,” Navarro said.

Public Ministry investigators found the inferno started with small simultaneous blazes near Lake Penuelas, in the port city of Valparaiso next to Vina del Mar. Hot and windy weather quickly spread the flames.

“There were approximately four outbreaks, equidistant from each other,” prosecutor Osvaldo Ossandon said.

Materials used to start the fire were found in the house of one of the suspects, he said. Investigators were also probing potential links to other arson incidents.

It was unclear what the motive was for the arson.

“All of us … knew that this had been an intentional attack,” Vina del Mar Mayor Macarena Ripamonti said. “Today we can have that degree of certainty.”

Firefighters had been unable to reach the fire due to a lack of roads or were stuck on narrow city streets lined with charred cars.

“This is, first and foremost, an act of justice and reparation to those who lost their lives in the fire, to their families, to those who lost all their property, their sources of work and struggle to this day,” Interior Minister Carolina Toha said.