Washington authorities have arrested a 37-year-old man on a first-degree arson charge in connection with the Old Trails Fire, one of several wildfires that have destroyed hundreds of structures and forced tens of thousands of people to evacuate the Spokane area. The largest of the three blazes burning around the city remained uncontained Monday as crews worked to slow its spread.

Aaron F. Farinacci was taken into custody Monday after investigators with the Spokane County Sheriff's Office and the Washington Department of Natural Resources developed probable cause, according to the sheriff's office. Officials said citizen tips, along with information from Airway Heights police officers and sheriff's deputies who responded to the initial call and conducted evacuations, helped lead investigators to Farinacci.

The sheriff's office described Farinacci as a convicted felon from Arizona but said investigators found no documented criminal history involving fires. When deputies detained and searched him, authorities said they found a butane lighter and waterproof matches. Farinacci was booked into the Spokane County Jail and was being held on $1 million bond.

Detectives obtained an arrest warrant for Farinacci and a search warrant for his residence in the 2800 block of West Elliott Drive. Deputies served the warrant Monday and arrested him without incident. Spokane County Sheriff John Nowels said investigators would continue looking into Farinacci's background. «We will be looking into any other crimes Mr. Farinacci may have committed in the past,» Nowels said during a news briefing. He added that first-degree arson was the charge supported by probable cause at that stage and cautioned that the case could change as authorities gathered additional evidence.

Investigators have not connected Farinacci to the two other major fires burning in the Spokane area, the Autumn Lane and Fairview fires. The Old Trails Fire was first reported Saturday near North Old Trails Road and West Euclid Road. It became the largest of the three fires and remained uncontained Monday, according to authorities.

The three fires have collectively destroyed at least 700 structures and prompted evacuation orders affecting approximately 67,000 people as of Monday. More than 1,000 firefighters were battling the blazes. The fires have spread rapidly amid drought, unusually high temperatures and strong winds, creating dangerous conditions for residents and emergency crews.

Washington Gov. Bob Ferguson declared a statewide wildfire emergency Saturday in response to those conditions. The declaration also imposed a statewide prohibition on most outdoor and agricultural burning through Sept. 30.

The investigation is ongoing, and the emergency remained active Monday with the largest fire still uncontained. Sheriff's officials said the charge could be revised as additional evidence is gathered, and investigators are checking whether Farinacci may have been involved in other offenses.