Unexplained , intermittent failures persist despite repairs , Metro official says . The cause of a deadly Washington Metro subway crash last month remains a mystery , with one problem identified by investigators persisting even after engineers replaced a key part that was believed to be faulty , a top Metro official said Tuesday . NTSB recalls loud bang , `` accordion-like '' collapse of floor , screams . Delegate chides Metro for making high-cost , `` impossible '' recommendations . Nine people killed , scores injured in June 22 crash near Fort Totten Red Line 's station .
Unexplained , intermittent failures persist despite repairs , Metro official says . NTSB recalls loud bang , `` accordion-like '' collapse of floor , screams . Delegate chides Metro for making high-cost , `` impossible '' recommendations . Nine people killed , scores injured in June 22 crash near Fort Totten Red Line 's station .