FORT WASHINGTON, Md. (CBSDC/AP) — Prince George’s County police say a family of five is in critical condition after being exposed to high levels of carbon monoxide in their home.

Authorities were first called to the family’s home after their two-year-old son fell out of bed and began seizing. He was taken to the hospital by ambulance while some family members stayed behind.

At first, doctors believed the boy suffered an injury. However, an alert nurse suspected the carbon monoxide poisoning when he learned the family members who remained at the house could not be reached via telephone.

Doctors at Children’s National Medical Center in Washington the dispatched police to the Fort Washington home where the family was found unconscious about 12:30 a.m. Tuesday.

The family of five, including two parents and three children, were taken by helicopter to a Baltimore hospital where they received hyperbaric oxygen treatments.

“The family basically could have not made it from carbon monoxide toxicity,” said Dr. Shireen Atabaki who treated the first child. “This happens. It’s a silent killer.”

Police say they believe a malfunctioning natural gas furnace in the home was to blame for the carbon monoxide.

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