Chicago, IL — Two people died and four other people were hospitalized, including three children, after a carbon monoxide leak Friday afternoon at a home in the Little Village neighborhood.

Chicago Fire Department Acting Deputy District Chief Barry Garr said firefighters responded to a home in the 2800 block of West 22nd Place on Friday afternoon, after a neighbor reported a gas smell.

When firefighters arrived, they forced their way into the home, they found elevated carbon monoxide levels throughout the home. Two people, a woman in her 70s, and a woman in her 50s, were found dead in the basement, Fire Department officials said.

Four other people, including three children, were found on the first floor of the home, suffering from symptoms of carbon monoxide poisoning, according to Garr. Those four were taken to Stroger Hospital of Cook County for evaluation and treatment, and their conditions were stabilized.

Garr said carbon monoxide levels inside the home were measured at 200 parts per million or higher, far above what is considered safe. According to Garr, carbon monoxide levels above 10 parts per million will trigger standard carbon monoxide alarms.

According to Garr, the home did not have any carbon monoxide detectors.

“You’ve got to make sure that CO detectors are on all levels in here, and they our first line of defense to protect us from any type of event such as this,” he said.

Garr estimated that the problem inside the home likely started sometime overnight, based on what firefighters found inside.

“The problem could have been anywhere from, I’m going to say, maybe in the last 12 to 15 hours,” he said.

The cause of the carbon monoxide leak was not known as of Friday afternoon, according to Garr.

Although the home has a heater in the basement, Garr said it’s unclear if it caused the elevated carbon monoxide levels.

It will be up to the gas company and the Chicago Police Department to investigate the cause of the leak, Garr said.