Metrorail said passengers could see delays on the Yellow and Blue lines Friday morning after brief single-tracking near the King Street-Old Town station.
The single-tracking was caused by a signal problem.
It was resolved quickly, but as of about 8:40 a.m. Metro was warning that delays could continue, particularly on the Yellow and Blue lines.
Green Line trains also could see residual delays, Metro said.
Metro's maintenance needs have been a huge issue for Metro lately. The agency's new general manager, Paul Wiedefeld, has developed a massive maintenance plan called SafeTrack.
But just this week Metro had to push back the plan after federal regulators said three track locations needed urgent attention. Now, Metro is contemplating a 16-day closure of a stretch of the Blue, Orange and Silver lines for repairs.
That stretch is on the Blue and Silver lines between Eastern Market and Benning Road and the Orange line between Eastern Market and Minnesota Avenue for repairs -- the other end of those lines from Friday's disruption.