MILLINOCKET – Arson caused the destruction of a trailer on Iron Bridge Road on Labor Day, the State Fire Marshal’s Office said Wednesday.

Sgt. Stu Jacobs of the State Fire Marshal’s Office made that determination after reviewing the fire scene, collecting evidence and interviewing firefighters and witnesses Tuesday.

“We have a suspect, and we plan on filing the appropriate charges today or tomorrow,” Sgt. Tim York, Jacobs’ supervisor, said Wednesday.

York declined to identify the suspect.

A spokeswoman for the Penobscot County District Attorney’s Office in Bangor, which covers the Katahdin region, said the office had not received a warrant application Wednesday.

Fire Chief Wayne Campbell called investigators to the scene Monday because the man who lived in the trailer, Richard Day, 52, told them he had fallen asleep while smoking in bed, Campbell said.

Campbell knew that Day has a history of mental illness and suspected Day’s explanation didn’t fit with the heavy amount of flame and total destruction of the trailer and the short time it took firefighters to get to the scene.

When firefighters arrived at the scene at about 2 p.m., the fire had almost totally engulfed the trailer and Day, who has suffered from schizophrenia, was walking toward downtown, Campbell said.

Day also had been involved in two car accidents on Penobscot Avenue and Central Street last week after which he was hospitalized briefly and charged with operating a motor vehicle while under the influence of intoxicants and leaving the scene of an accident.

Day was taken into protective custody Tuesday after Millinocket police Detective Ron McCarthy found him dodging traffic on Central Street. It took as many as nine men, counting McCarthy, to take Day into custody.