Detroit, MI – WDIV-TV – Parishioners of a local church were admitted to a hospital after they were exposed to carbon monoxide Sunday, Local 4 reported.

People attending a service at the Bethlehem Assembly Church on Mack Avenue in Detroit went to the emergency room at Detroit Receiving “feeling dizzy, nauseated, (and with) shortness of breath,” said Cloria Farris, registered nurse.

Three people were admitted to the hospital and treated in a hyperbaric chamber, which reportedly removes toxic gases from the bloodstream.

Farris said the hospital initially believed there were more parishioners exposed.

“We got a phone call that, at first, it was, like, 23 people that were possibly suffering from carbon monoxide poisoning,” Farris said. “I think maybe 10 to 11 came to the ER. Of those, three were admitted to the burn center.”

The three patients are reported in good condition.

It was not known where the carbon monoxide was coming from in the church, Local 4 reported. Officials were not available for comment on Monday.

Experts advise residents and building owners to inspect the furnace before heating it up for the first time of the fall or winter season.