Another too-long train went into service on the Metrorail system early this morning, and WMATA is once again investigating how it happened. WTOP reports that a 10-car train was able to travel from Branch Avenue to the Waterfront-SEU station before being taken out of service. Five employees have been removed from service for routine drug and alcohol testing as a result of the incident. Back in March, a 14-car train briefly went into service on the Orange Line, though the mistake was caught before it left its first station.