Saratoga Springs, UT – Twelve people are being treated at local hospitals on Tuesday night after they were poisoned by carbon monoxide.

Construction workers at an office building in Saratoga Springs fell ill Tuesday afternoon and contacted authorities, said Kenny Johnson, deputy fire chief in Saratoga Springs.

Fire crews determined the workers were suffering from carbon monoxide poisoning after operating concrete equipment inside the building, Johnson said.

Nine workers were taken to three different hospitals because the hyperbaric facilities needed for treatment have limited capacity. Three more workers were well enough to transport themselves to the hospital, said AnnElise Harrison, communications director for Saratoga Springs.

Fire crews were able to ventilate the building, Johnson said. He noted that Lehi Fire and Unified Fire Authority assisted with treating patients and clearing the affected building.