More than 200 employees were displaced from a four-storey building in the downtown core Wednesday afternoon after several occupants detected the smell of diesel and began to feel ill.

Shortly after noon, members of the Calgary Fire Department were deployed to the North-West Travellers Building in the 500 block of 1 St. S.E. following reports of noxious fumes by employees on the lower floors.

Firefighters checked air quality and carbon monoxide levels throughout the building and determined the source of the fumes to be the testing of a back-up generator in a neighbouring building.

Carbon monoxide has not been detected within the building.

The CFD Hazardous Materials team will remain on scene until air quality is deemed safe. Employees are expected to be permitted to return to the building within the hour.