Metro said Sunday that “stuck brakes” caused one of its trains to send smoke skyward while traveling near the Ronald Regan Washington National Airport, prompting delays on the Blue and Yellow lines amid the Thanksgiving travel crush.

Dan Stessel, a spokesman for the transit agency, said the involved train was not carrying any passengers when the incident took place around 10:43 a.m. Sunday, and no one was injured. The train was empty, Stessel said, because it was being moved to another part of the Metro system.