Des Moines, IA – One person died Friday morning of carbon monoxide poisoning at a Des Moines home because of an issue with a furnace in a garage, authorities say.

Two men were working on a car in a garage in the 400 block of Hull Avenue late into the night Thursday, said Des Moines Fire Capt. Gary Ramquist. Earlier, they fixed an issue with a gas furnace in the garage, he said.

One man was later treated at hospital for carbon monoxide poisoning and told authorities the other man may also be suffering from carbon monoxide poisoning. Around 5:45 a.m., firefighters found the other man dead in the garage, Ramquist said.

“If you’re going to do any work on an HVAC system, make sure qualified personnel are working on it,” Ramquist said.