A two-vehicle accident injured four people Wednesday night and forced authorities to shut down Suitland Parkway, D.C. police said.

Two people were found pinned inside a vehicle and two others were in life-threatening condition following the crash on the parkway near Naylor Road about 8 p.m., said Officer Paul Metcalf, a spokesman. Authorities shut down the highway in both directions.

Police were investigating the cause of the crash.