Chicago, IL – Two people were hospitalized in critical condition with carbon monoxide poisoning Tuesday in Gresham on the South Side.

Authorities were called about 7:45 p.m. to a home in the 8500 block of South Ada Street, according to Chicago Fire Department officials.

Crews detected “lethal” levels of carbon monoxide within the home, and two adults were taken to Little Company of Mary Hospital in critical condition, officials said.

Someone in the home was using a generator for electricity, officials said. A cat was also found dead inside.