A carbon monoxide leak at the Woodmen Tower caused an evacuation over the lunch hour on Thursday. Around 3 p.m., fire investigators allowed employees back into the tower. The World building will remain evacuated until Friday.
Official CO detectors were at 60-parts-per-million. Firefighters say they typically evacuate a building when the number is 9-parts-per-million.
The problem originated in the boiler room of the World building, which is connected to the tower. Investigators say the boiler had exhaust problems.
Two people were taken to the hospital with CO poisoning symptoms.