Metro Transit Police announced on Thursday they have joined in on an internal administrative investigation into last month's East Falls Church Metro derailment.

Metro General Manager Paul Wiedefeld said officials decided to open the investigation after safety investigators voiced concerns following interviews with Metro workers, reviews of inspection reports and video recordings.

"While Safety Department investigations determine cause and accountability, it is even more important to understand if other issues must be addressed with the way track inspections and maintenance have been conducted," Wiedefeld's statement said.

Two former federal prosecutors were also hired as special investigators to support the internal review.

"The public has a right to know that the tracks on which their trains run are being properly inspected," Wiedefeld said. "The information uncovered to date raises potentially serious concerns, and we will take all actions necessary to get answers and hold people accountable."

SafeTrack, Metro's program working to "address safety recommendations and rehabilitate the Metrorail system to improve safety and reliability."

The July 29 derailment ruined the morning commute for a slew of Metro commuters, affecting Orange and Silver line riders. A train derailed at the East Falls Church station platform. One man was injured.