A system-wide signal problem caused delays on all six lines of the Metro system Thursday morning.
The Rail Operation Control Center lost the ability to remotely control switches where the rail lines converge Thursday morning, Metro spokesman Dan Stessel said.
Workers had to manually switch the lines, causing delays toward the end of the morning rush. Riders were told to expect delays of up to 20 minutes, but many riders on Twitter said the delays were much longer.
"Delays far worse than 20 min, and as usual trapped underground out of cell range with no info from driver,"Zach Olson wrote on Twitter.
The signal problem was resolved at about 10:45 a.m., but Metro said riders should expect residual delays.
The cause of the signal problem is under investigation, but Metro says it appears to be an IT issue.