[This post has been updated]

Metro experienced severe delays on the Red Line Thursday, causing severe crowding and prompting transit police to briefly close the entrances at Gallery Place station.

Riders flooded Twitter with angry comments and photos and video of crowded platforms.

Two problems sparked the chaos, according to Metro. One train had a brake issue at Judiciary Square, but by the time it was moved off the line, delays were already building. There was also a signal problem near Woodley Park. Train operators had to get verbal permission to proceed along the line, Metro spokesman Dan Stessel said.

“If one thing goes you can see how it unravels,” he said.

Why do the problems seem to happen most frequently during rush hour?

“The probability of a train encountering an issue is higher when there are many more trains on the railroad,” Stessel said. “This equipment isn’t where it needs to be. It wasn’t maintained for years. We are in the process of digging out of that hole. It is not going to be immediate. It is going to take time.”