MYSTIC, Conn. (WTNH) — Mystic firefighters treated hotspots Tuesday, two days after a four-alarm fire engulfed two commercial building and one multi-family home along the Mystic River. 

Fire Chief Anthony Manfredi said it’s going to be a lengthy investigation due to the size of the fire at Seaport Marine. It could take about a week before authorities learn the cause. 

“It’s going to burn for several days, because we can’t get down to the root of the source of the ignition,” Manfredi said. 

Manfredi said it took more than four hours for 18 departments and more than 60 firefighters to put out the flames. Now, officials are taking steps to learn what happened. 

“We photograph the scene first, and then we go in and talk to a lot of the witnesses that may have seen something,” Manfredi said. “We go around and try to get some video.” 

Officials are also using drone video. 

Clean-up crews were at the scene, removing oil out of oil tanks and picking up debris. The Connecticut Department of Energy and Environmental Protection was also monitoring for asbestos.

Clean-up crews were on-hand removing some oil out of oil tanks. 

Crews are working with Connecticut’s Fire Marshal’s Office and the Stonington Police Department.  

“We’re going to have to methodically take off some metal to get down to the root of the fire and what was burning,” Manfredi said.

Anyone with video from the early stages of the fire is asked to give it to Stonington police.