No cause of the smoke has been determined. Around 5:40 p.m., Metro spokeswoman Caroline Laurin said that the smoke has now cleared from the station. That is at least in part due to the tunnel fans that Metro workers turned on, she said. But in the event that the fire was caused by an electrical malfunction – which workers have not yet confirmed – the smoke may also have abated because Metro shut down the third rail at L’Enfant Plaza.