A fatal, officer-involved shooting has taken place at the Potomac Avenue Metro station in Washington, D.C., police announced Thursday.

The shooting occurred after officers responded to reports of an unauthorized person in the tunnel. The suspect was pronounced dead at the scene, and all the responding officers were accounted for and unhurt, according to a tweet from the city's Metro Transit Police.

The incident took place in the tunnel, around 400 feet from the station, police said. A homicide unit is on the scene, according to the Washington Post.

Metro says that the Orange, Blue and Silver lines are single-tracking between Eastern Avenue and Stadium-Armory, and that passengers should expect delays in both directions.

The officer who fired is on paid administrative leave, which is standard procedure, NBC Washington reported.

This is the second death in the D.C. Metro this year. In Jan. 2015, an arcing third rail continued to be supplied with power for 30 minutes after smoke was reported in a tunnel. One person was killed by smoke coming from the rail in that incident.

This is a developing story. Check back for updates.