Tuscola County, MI – Three people survived a potentially lethal exposure to carbon monoxide in their residence near Vassar late Monday.

Michigan State Police and the Vassar Fire Department responded with an ambulance to the 5000 block of West Sanilac Road around 11:20 p.m. Emergency crews didn’t recognize the signs of carbon monoxide poisoning initially and left the scene.

One of the residents later collapsed and fell unconscious, leading to a second 911 that brought rescuers back to the scene, police say. All three people were rushed to an area hospital with potentially deadly levels of carbon monoxide in their bodies. They are expected to survive.

Investigators say the residents live in an older mobile home, which lost power after the weekend wind storm. They were running a gas-powered generator outdoors and covered it with metal sheets.

Firefighters and Consumers Energy crews aired out the house and moved the generator to clear toxic gases from indoors.

Michigan State Police warn everyone to be careful with gas-powered generators during power outages. Symptoms of carbon monoxide poisoning include a dull headache, weakness, dizziness, nausea or vomiting, shortness of breath, confusion, blurred vision and loss of consciousness.

Residents are advised to place a carbon monoxide detector on every level of their homes.