Authorities have determined that a fire that ripped through a Gilbert condominium complex was “incendiary,” or intentionally set, and a $30,000 reward has been posted for information leading to the arrest and conviction of the arsonist.

The arson determination was reached after “a systematic fire scene investigation” that included the Gilbert fire and police departments, with the assistance of the federal Bureau of Alcohol, Tobacco and Firearms.

A dog trained in finding flammable liquids uncovered evidence of arson at the scene, said Deputy Chief Josh Ehrman, a Gilbert Fire Department spokesman.

“They pulled everything apart,” he said. “Based on what they found, they can call it an arson.”

The fire, which started at about 7 p.m. on Oct. 15, destroyed eight buildings at the Via Sorento Condominiums, under construction at 240 W. Juniper, just south of Guadalupe and Gilbert roads.

“Thirty investigators have been working around the clock to conduct approximately 200 interviews, a systematic fire-scene examination, a review of witness videos and photos and all viable accidental and natural fire scenarios have been hypothesized, tested, and eliminated,” according to a press release issued late Thursday afternoon by the Town of Gilbert.

The press release said damages from the arson fire are estimated to be over $10 million.

Authorities have posted a $15,000 reward for information leading to the arrest or conviction of anyone responsible for the fire. D.R. Horton, the Texas-based builder that owns the project, has posted an additional $15,000 reward.

Ehrman said fire investigators are still looking for tips from the public that would help them identify and interview a young man who was seen near the scene of the spectacular Via Sorento condominium fire on Saturday night.

Gary Hildebrandt, a Gilbert Fire Department spokesman, said that the young man is considered a person of interest that authorities want to identify and interview, but that there is not enough evidence to consider him a suspect.

The person of interest was described as a while male 16-22 years old, 5-feet-7 to 5-feet-10, wearing a maroon Arizona State University hoodie-style sweatshirt, dark shorts and Van’s-style shoes. He has shaggy, long brown hair just below his ears, long bangs and no facial hair.

“It could be related or totally unrelated,” Hildebrandt said. “There were witnesses who said they saw an individual matching this description shortly before the fire. We just want to talk to him.”

The fire was so intense that it consumed a car nearby, melting the tires.

About 150 firefighters from the Gilbert, Mesa, Chandler and Superstition fire departments were able to save at least two buildings that were under construction on the north side of the complex and two on the south side that were nearly finished, Hildebrandt said.

Firefighters also saved some occupied units to the south and evacuated about 20-25 residents Saturday night because of high levels of potentially deadly carbon monoxide in the area, he said. The residents were allowed to return home Sunday morning.

Some buildings at the scene were damaged but still standing, but others were reduced to a pile of rubble.

“We started evacuating and protecting the occupied apartments right away,” Hildebrandt said. “There was a very, very heavy fire load because there was a lot of exposed wood. It was in the framing stage.”

The Via Sorento fire was second in Gilbert this year at a large apartment complex that was under construction. The first one, the Civic Center fire, was on April 23. It was a much larger fire at a complex not far from Gilbert Town Hall, destroying 17 buildings.

Hildebrandt said an investigation eventually determined that the Civic Center fire was accidental, caused by a construction worker who was using a torch while installing some roofing.

Anyone with information is asked to call Gilbert Fire investigators at 480-503-6346 or to email them at fireinvestigations@gilbertaz.gov.