Metro officials are monitoring train control circuits at the Foggy Bottom Metro station and five other stops after the system failed to detect the presence of trains, the Washington Post reported earlier this week.

The Metro system has come under intense scrutiny following a Red Line collision last month that killed nine passengers. The circuit at the site of the accident had been malfunctioning since September 2007, according to the National Transportation Safety Board. Metro officials have now identified six problem circuits, including one located at the Foggy Bottom stop, and disabled some of them, according to the Post’s report.

Disabling the circuits causes delays up and down the lines because the trains must pass through one at a time at maximum speeds of 15 miles per hour, according to the Metro Web site. Trains still communicate with and are visible to Metro controllers in the Operations Control Center, according to the site.

Metro has posted a video taken at the command center to illustrate how trains pass through disabled circuits.