12: 50 p.m.: The suspicious package has been cleared, according to D.C. emergency officials. The District Department of Transportation reports that the tunnel has reopened.
12:30 p.m. Update: D.C. emergency officials are also reporting that several vehicles have been involved in an accident in the northbound tunnel. EMS crews are evaluating people at the scene.
Original post: D.C. emergency officials report that the Third Street Tunnel is closed in both directions due to a police investigation of a suspicious package at Third and D streets NW.