Times Observer file photo A firefighter keeps an eye on the April 2021 Cobham Hill wildfire in Watson Township. The cause of that fire has been ruled accidental while a fire in Glade Township has been ruled arson.

The cause of one of two Warren County wildfires that burned more than 200 acres each last April has been determined to be arson.

On Thursday, Pennsylvania Department of Conservation and Natural Resources Cornplanter District Forester Cecile Stelter and Fire Forester Jay Lindemuth announced the findings.

The Hemlock fire resulted in the burning of 259 acres in Glade Township from Thursday, April 8, through Wednesday, April 14.

“Based on the investigation that Jay and our special investigator (Terry Smith, of DCNR in Harrisburg) conducted, we have determined the cause of that fire was arson,” Stelter said.

The other large wildfire — the Cobham Hill fire in Watson Township — consumed at least 227 acres. It was ruled accidental with a specific source of “utility infrastructure.”

“The investigation took us back to the point of origin,” Stelter said. “There was some utility infrastructure right there.”

The two fires were the largest in the state in 2021. The Cornplanter District in northwestern Pennsylvania, had the fourth most fires — 122 — but easily the largest number of acres burned — 753 — among the 20 districts in 2021. No other district had over 425 acres burned.

The two April 8 fires in Warren County represented well over half of the burned acres in the county for the year and more than any other district in the state.

No injuries were reported as a result of the two fires.

“Our priority is life, property, and resources,” Stelter said. The Hemlock fire “endangered people’s homes” and firefighters’ lives.

“We take this very seriously,” she said. “A cause is determined for every wildfire that is suppressed and/or investigated in Pennsylvania.”

“We investigate every fire the same way,” Lindemuth said.

There is a systematic methodology to the work.“We take the evidence at the scene,” Lindemuth said. “Fires will tell the story.”

“We know what the causes are,” he said. “We start ruling them out.”

Unlike in structure fires, where the starting point is often the hottest, the fire at the point of origin in a wildfire is usually less intense.

The investigators traced the Hemlock fire back to its origin. A DCNR reconnaissance plane was over the scene early on in the fire, so they had a good idea of where it started without doing any of the legwork. “We were able to determine (from the reconnaissance) down to five acres in a 200-acre fire,” Lindemuth said.

“We knew where the head of the fire was when they started suppression efforts,” Stelter said.

Given records about the wind direction and the burn patterns, they tracked the fire.

They found no utilities, no sign of campfires, debris fires, and there was no lightning on the day it started. The investigators found nothing pointing to other causes.

“All other causes were ruled out,” Lindemuth said.

Arson is not investigators’ first thought in a wildfire. “That’s really the last cause that I have in the back of my head,” he said.

The investigations are thorough. Lindemuth said there have been burned heads of matches and staples from matchbooks found at the origins of other fires.

No accelerant was found at the origin. Neither was a device that could have started a fire.

That there was no evidence was part of the evidence.

“The fact that there isn’t any evidence is part of the conclusion,” Stelter said.

“This particular individual put flame to the fuel that was there,” Lindemuth said.

Why someone set the fire is a mystery. “We don’t know that, yet,” he said.

The investigation is open and ongoing, Stelter said.

There have not been any charges filed in the case and officials are looking for information.

“We are working with Crime Stoppers,” Stelter said. “If anyone has any information relating to the Hemlock fire” they may call the Bureau of Forestry office or the anonymous Crime Stoppers line.

They are also asking that anyone who sees anything suspicious this fire season — which will be starting soon — contact the bureau.

Lindemuth shared the findings at the Warren County Fire Chiefs Association meeting Thursday evening.