Updated

More than 50 people were taken to a hospital Saturday after high levels of carbon monoxide were detected at a high school pool during swimming lessons, police said.

The 55 children and adults were transported to Beaumont Hospital (search) after many of those inside Dondero High School (search) were sickened, Royal Oak (search) police Sgt. Barry Gale said. Police were called after 10 a.m. and laid those sickened on a sidewalk outside the school, he said.

It wasn't clear whether all those taken to the hospital were sickened. Those being treated were listed in good condition.

Gale said testing by the fire department determined high levels of carbon monoxide inside the pool area. He said it was believed to have been caused by a malfunctioning furnace.