Fire destroyed a vacant building Sunday at an old seed processing plant in Mount Vernon.
Fire Marshal Steve Riggs said the wooden structure was too dangerous to allow firefighters inside so they poured on water from the outside.
The Skagit Valley Herald reports police arrested a person of interest on the roof as the fire broke out. He was questioned and released Sunday night. Police spokeswoman Shannon Haigh says he's a transient.
The Alf Christianson Seed building was vacated two years ago and has no electricity.
The 10-acre site has been considered as the location for a new Skagit County Jail. It sits along railroad tracks, and freight and passenger trains were delayed when fire hoses crossed the tracks.