STOW -- More than 40 people were treated, about two dozen at area hospitals, after high levels of carbon monoxide were detected inside a bowling alley.

About 25 people were taken to eight different hospitals after Stow Fire Department crews triaged about 80 people who were inside Sto-Kent Family Entertainment around noon.

"People were falling, dropping like flies," said Ken Riehl, a bowler who was inside at the time.

The regularThursday competition was interrupted by strange and sudden illness.

"One person was finished and walking out and she just went down. That started to wake us up," said Riehl.

The Stow Sunshiners bowling league says first members assumed it was something as simple as low blood sugar, but to be safe, they called 911.

The woman was up and walking around when they arrived, but fire crews quickly determined it was carbon monoxide.

"It is certainly serious. It is what we would consider immediately dangerous to life and health," said Capt. Mark Stone with the Stow Fire Department.

Levels reached about 350 parts per million. Zero is normal. Anything over 50 ppm can be threatening.

"Older people are certainly more compromised by CO," said Stone.

"I said, take care of the other people first because I didn't feel anything," said Riehl, "Other people, they were just, they were fine and then suddenly they were not fine. They started to fade."

The cause is still under investigation, and the building closed for now.

The owners told Channel 3 News they did not have a carbon monoxide detector inside, but the fire department says most devices wouldn't work properly in a space this size.