Chilean authorities have arrested a firefighter and a forestry worker on suspicion of starting the fire which killed at least 137 people in February.
One of the men was employed by the National Forestry Corporation which is responsible for fighting forest fires, police director Eduardo Cerna said.
The suspects have been remanded in custody, charged with arson resulting in death.
The fire – was country’s deadliest – devastated the Valparaíso region, which is more than 122km (75 miles) from Chile’s capital, Santiago.
Officials allege that several fires were started simultaneously, after which high temperatures and wind caused the flames to spread.
More than 16,000 people were affected by the fire which destroyed homes and devastated the region, which is home to Vina del Mar, a popular holiday destination.
Commenting on the arrest of the firefighter, Vicente Maggiolo, commander of the 13th Fire Company in Valparaiso, told local media: “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.”
Prosecutor Osvaldo Ossandón said: “There were approximately four outbreaks, equidistant from each other.”
He said materials used to start the blazes were found in the home of one of the suspects, adding that investigators are examining possible links to other arson attacks.