Five people were taken to the hospital Wednesday after a carbon monoxide incident at a building in Salem, Massachusetts.
The incident took place at the sprawling Shetland Park complex on Congress Street. Authorities said one person became unconscious, prompting a call to first responders who evacuated the entire fourth floor.
"The fourth floor has been totally evacuated. The rest of the building remains," Salem Fire Lt. Peter Schaeublin said. "There were no readings on the other floors."
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Two people were taken to an area hospital then transferred to Massachusetts General Hospital for treatment in a hyperbaric chamber.
"They did a test on everyone that was on the fourth floor including firefighters that were trying to get people out of the building," Schaeublin said.
Everyone was expected to recover.
Crews spent the afternoon working to ventilate the building.
Investigators said an imaging and fiber optics company is located where the incident occurred.
"It has been ventilated now but they still have to figure out what was the source and why it happened," Schaeublin said.
A heating unit is believed to be the source of the carbon monoxide.