One lane of traffic was shut down on Main Street for about an hour today while the Westport Fire Department pinpointed a source of smoke in buildings along the busy downtown area.

Shortly after responding at 5:14 p.m., firefighters determined that the cause of smoke was a faulty portable air conditioning unit in the basement of Eileen Fisher's Clothing store, at 160 and 166 Main St. Fisher's store and Achorn Pharmacy were ventilated and firefighters -- four engines, a rescue truck and the shift commander's vehicle -- cleared the scene at approximately 6:30 p.m.