Metro crews are inspecting the agency's oldest rail cars daily and outfitting them with special Kevlar protections in the wake of explosions on an out-of-service Red Line train last month.

The Red Line train caught fire during the evening commute on May 14. The train had offloaded its riders at Takoma just moments before. Then, one stop later, the train caught fire amid three explosions at the Silver Spring station.

Metro officials said Thursday that the cause of the explosions was due to a cleat that held a hose breaking off a 1000 series train. That caused the hydraulic brake hose to fall down so it rested on top of a power cable. Over time, the protective covering wore down, causing the fire and explosions.

Metro mechanics have since inspected all of the 1000 series rail cars and found "less than a dozen" with problems, said Rob Troup, Metro's head of operations. But he said the agency's other rail cars were not affected as they do not use hydraulic-style brakes.

All of the 1000 series cars will have new Kevlar sheaths placed over the equipment to protect them from such friction, he said. The work is ongoing, but he did not have a timetable on when it would be finished. Metro maintenance crews had not been inspecting that aspect of the trains in their daily and monthly checks, according to the agency, but the trains are now be inspected daily for similar problems.