Renton, WA – An apartment complex was evacuated Thursday afternoon in Renton after sensors detected elevated levels of toxic carbon monoxide gas inside the building, emergency officials said.

Firefighters and medics were dispatched to the scene, at 95 Burnett Ave. South in Renton, in response to an automatic alarm there.

First responders found an increased level of carbon monoxide and immediately began evacuating residents from the complex.

Additional crews were called to the scene to assist with the evacuations.

Investigators are now searching for the source of the toxic fumes.

Carbon monoxide is a colorless, odorless gas that can kill. It is commonly produced by combustion from engines or stoves. Symptoms of carbon monoxide poisoning include headache, dizziness, weakness, vomiting, chest pain and mental confusion.