AUBURN, Wash. -

Police suspect a disturbing discovery in Auburn may be evidence of a crime.

An off-duty federal agent driving down Peasley Canyon Road Wednesday afternoon noticed a fire in the woods and stopped with his extinguisher. A man at the fire sped off in a dark SUV before the agent discovered what he was burning: blood-soaked carpeting, towels and flooring.

KIRO reports police are investigating -- having the blood tested at a crime lab and asking for leads from the public.

Cmdr. Dave Colglazier says detectives presume the blood came from a crime scene, but they haven't found it yet.