DALLAS (CBSDFW.COM) — DART officers are investigating after approximately 20 people reported feeling nauseous at DART headquarters Thursday afternoon.

Around 1:12 p.m. Dallas Fire-Rescue was assigned to a 911 call for a “foul odor” coming from the vents of the DART Administrative Office, located at 1401 Pacific Ave. in downtown Dallas.

DART officials said there is no available information on the source of the odor, but an unspecified number of employees have since reported smelling it. They have since been moved to a different room in the building while the investigation continues.

No one has been transported to a medical facility.

In caution, the DART Customer Service Center will be closed until noon Friday.