Authorities have launched an investigation into possible arson after firefighters successfully knocked down the last of four wildfires that erupted in Suffolk County on Saturday.

The wildfires, which began around 1 p.m. along Sunrise Highway, led to a State of Emergency, with fire crews working through Sunday to prevent further spread.

More than 90 fire departments, EMS agencies, and the National Guard battled the blazes, which sent heavy smoke billowing for miles, forcing temporary road closures on Sunrise Highway and causing major disruptions for hundreds of drivers.

Fire officials continue efforts to fully contain the Westhampton Pines fire, which, while 100% knocked down, remains only 22% contained after burning more than 400 acres.

According to Suffolk County Fire Rescue and Emergency Services Commissioner Rudy Sunderman, a fire being “knocked down” means all visible flames have been extinguished, whereas “containment” refers to the creation of a fire break around the perimeter to prevent reignition and further spread.

Local business owner Mark Cirillo watched in disbelief as towering flames surrounded his property on Old Riverhead Road in Westhampton.

As the investigation into the cause of the fires unfolds, officials are urging the public to remain cautious and report any suspicious activity that could be linked to arson.