A former Snohomish lumber mill that was believed to be filled with mattresses and computers caught fire Wednesday morning.
The fire started around 1 a.m. It took firefighters about three hours to knock down the fire.
The Department of Ecology was called to the scene due to concerns over the materials that were burning inside the warehouse.
Firefighters began clearing the scene just south of the Snohomish River near Airport Way around 4 a.m. Some remained to put out hot spots.
Officials do not believe anyone was inside at the time.
The warehouse is on former Seattle-Snohomish Mill property. It was Snohomish's last mill, which shut down in 2015.
This is a developing story. Check back for updates.