Watertown, MA – Six people, including three minors, were taken to a hospital after high levels of carbon monoxide were found inside a Watertown apartment building Wednesday night.

The incident was reported at the Riverside Condominiums on River Street.

Resident Mike Kolk told NewsCenter 5 that he called the landlord after smelling a strange odor from the basement. He said he went into the basement to investigate and found the smell was coming from the furnace.

When firefighters arrived, they said they found high levels of carbon monoxide in the building, and tested tenants who were inside.

Some were found to be OK, while others were subjected to high levels of the carbon monoxide and were taken to hospitals.

Three adults and three children were taken to the hospital to be evaluated.

Resident John Robles said he just finished dinner when firefighters knocked on his door. His apartment tested safe, but he took his two dogs and evacuated.

“I don’t want to take any chances,” he said. “CO poisoning is serious.”

The scene cleared around 9:45 p.m. and people were allowed to go back inside the building.