PORTLAND, Ore. (KOIN) — Investigators believe the massive 4-alarm fire that damaged buildings in Northeast Portland on Monday was intentionally set.

Officials have not identified exactly what started it, but believe it was a human cause. They are looking at an “area of interest” northwest of the burn zone on 82nd Avenue.

Investigator Lt. Jason Anderson said they are “all hands on deck” collecting witness statements and data from the scene.

A map of the 4th-alarm fire in NE Portland on August 26, 2019. (KOIN)

Fire Chief Sara Boone said it was a “tremendous effort” on the part of firefighters, police and other agencies to get this fire under control. The heat, wind and low humidity Monday made it a difficult battle.

At least 40 units and around 120 firefighters responded and with only 165 operating personnel on each shift, this fire depleted Portland Fire and Rescue’s resources. Only 14 were left to respond to other emergencies.

Alexandra Lombardo was on her way back from the coast when she learned her home was on fire.

“I jumped out of the car, moved some traffic cones — my main concern was that my cat was inside,” she said.

#BREAKING Portland Fire Bureau says cause of NE Portland grass fire that burned homes cars and other bldgs INTENTIONALLY SET #KOIN6NEWS #nePDXfire pic.twitter.com/koSO4HiBRb — Lisa Balick (@lisabKOIN) August 27, 2019

Her cat survived, but the fire reigniting in the attic destroyed most of what was inside.

4-ALARM FOLLOW-UP: Check out the damage to dozens of cars and a nearby business from atop @LumberyardMTB. Spared major damage, a co-owner tells me he now wants to raise money for the families in townhomes affected #KOIN6News pic.twitter.com/Bn3C57gIkM — Cole Miller (@ColeKOIN) August 28, 2019

Will Heiberg, one of the owners of Lumberyard, an indoor bike park, told KOIN 6 News he wasn’t sure he would have a livelihood to come back to.

“24 hours ago, I thought the whole block was going to go if not bigger,” he said. “If the wind had changed direction, a lot of things — this would be gone. I’m incredibly fortunate.”

Aside from smoke inside and water damage, the Lumberyard will be OK.

The fire also destroyed Grand Avenue Boxing Club, a non-profit gym. A trainer there said the few people inside the gym at the time were able to safely escape.

Omar Mohamed, who was hoping to get back in the ring, will have to wait.

“I come back and I see the building next to it was on fire, it’s honestly surprising and sad,” Mohamed said.

Courtesy @CarHelmets

People nearby told KOIN 6 they heard explosions as dozens of cars were consumed by the flames, as well. Chatman said that sound may have been the tires from about 50 cars on a lot that were burned.

Dozens of cars were destroyed in a 4-alarm fire in Northeast Portland fire on August 26, 2019 . (KOIN)

“I got on the scene and everything is up in smoke. Our cars, the oil, the fuel tanks were exploding,” Tristyan Mills said. “We were trying to pull cars out but within minutes it’s too hot, you can’t even be here. Shoes were melting.”

No one was injured in the fire.

Crews were on scene overnight and into Tuesday, hosing down any hot spots to prevent another flare-up.

“It just feels apocalyptic,” Heiberg said. “There are no words for it. This could’ve ended people’s lives.”

Anyone with information that may help investigators should send tips to Crime Stoppers of Oregon online or at 503.823.INFO.