Milwaukee, WI – Multiple people fell ill Tuesday morning after being exposed to high levels of carbon monoxide at a home in the city’s Old North Milwaukee neighborhood.

An official told WISN 12 NEWS that six children and three adults were being treated at a home on the 4400 block of North 37th Street, just south of West Ruby Avenue.

The children range in age from 3 to 17 years. All nine were transported to a hospital to be checked out.

Two dogs were also removed from the home, a Milwaukee police detective said.

Carbon monoxide can be deadly; it kills more than 400 people and puts more than 20,000 in the hospital each year. The gas is odorless and colorless, which makes it difficult to detect. CO is produced by gas generators, fireplaces, wood stoves, charcoal grills, gas heaters and furnaces, and kerosene heaters.