At least two dozen people became sick and complained of fumes at two West Side buildings, but officials can't determine what was wrong.
The mystery began at about 10 a.m. Thursday, when staffers at the Alivio Medical Center in Pilsen began complaining of light-headedness and nausea.
"I got a phone call from one of my managers that several people were complaining bout coughing, (being) teary-eyed (and having a) dry nose, and it was like hacking sensation in one area," said center spokeswoman Dora Garcia.
That building was evacuated and some of those who said they were sick were taken to another facility. Once there, even more people said they were feeling sick.
"We've checked all our patients. The (gas) readings were zero at both locations. Wwe then trasnported six patients with unspecified medical conditions in good condition to the area hospitals, and we have 17 patients refused on the scene," said Chicago Fire Department Asst. Commander Mark Levinson.
Hazardous Materials crews and fire investigators combed both buildings, even calling in the gas company and the city’s environmental department, but no one could find anything that could have cause the illnesses.
"There was absolutely zero carbon monoxide. They checked for a variety of chemicals and found no readings," Levinson said.
The facility was reopened at about noon after being aired out and getting the all-clear from officials.
The Alivio Medical Center employs about 70 people and sees as many as 125 patients every day.