RTD early Monday suspended all light rail train service between its Colorado, Ridgegate and Florida stations for "emergency maintenance."
RTD officials tweeted the alert about 7:30 a.m. Monday and included the notice prominently on its website rtd-denver.com.
Shuttle busses were offered to riders of the H, R and E lines.
At about 12:45 p.m. Monday, a spokeswoman said via email service from the H and E lines would resume by 1:45 p.m., but with "single-track between Colorado and Southmoor (stations), with 30-minute frequencies."
Several riders complained on Twitter about shuttle buses being slow and having to take Uber or Lyft rides.
On Wednesday afternoon , a R-line train derailed at Exposition Avenue and Sable Boulevard in Aurora. Rescuers treated 24 patients for minor injuries, three were transported to local hospitals for non-life-threatening injuries, according to an Aurora Fire department spokeswoman.
But Monday's closure was caused by contractors working on the lines Sunday who discovered more extensive work needed to be done, RTD Spokesperson Tina Jaquez said Monday.
"It wasn't related to the derailment," she said.
The investigation into the derailment is ongoing and the R-line service remains closed past that intersection.
"The repairs, and the investigation, are taking longer," Jaquez said.
Officials encouraged riders to sign up to receive alerts about service disruptions at rtd-denver.com.
This is a developing story and will be updated throughout Monday.
