Emergency responders converged on the Oppenheim Building Thursday morning around 11:30.
They cleared out all eight floors of the Lackawanna Avenue building.
Workers, including those in the Social Security office, were among the evacuees who had to abandon their jobs. "I was on a call and then all of a sudden the lights and the alarm system was going off and they just said that we had to leave the building," said Social Security Office employee Salina Senatore.
Pennsylvania Ambulance paramedic Bruce Beauvais said, "At the end we had a total of 11 patients who were, you know, evaluated on scene and two were transported for treatment." The two women who were sent to the hospital went there as a precaution.
UGI blames the minor gas leak on a faulty valve in the 8th floor heating area which has since been repaired.
Workers were allowed to return to the Oppenheim Building a little more than an hour after the gas leak scare.