Six people were killed when a passenger vehicle pulled into a work zone along the Baltimore beltway and struck construction workers there, Maryland State Police said Wednesday.

Troopers responded to the work zone on northbound Interstate 695 at Security Boulevard in the Woodlawn area around 12:40 p.m. for a report of a pedestrian crash, police said in a news release. Emergency medical service personnel pronounced six people, all of them workers, dead on the scene, and the driver of the car was taken to the University of Maryland Medical Center’s Shock Trauma Center, police said.

The preliminary investigation found that the vehicle pulled between the jersey walls of the work zone for unknown reasons and hit multiple workers before overturning, police said. The driver’s identity is unknown, police said. Late Wednesday, police said investigators believe a second vehicle that stayed on the scene may have been involved in the crash.

The crash closed the beltway in both directions for hours, snarling traffic along the west side of the highway that encircles the city. Baltimore County Fire Department officials called the crash “extremely serious” and asked drivers to avoid the area.

Baltimore County Executive Johnny Olszewski called the incident horrific.

“We offer our sincere condolences to the families, friends, and loved ones of those who have lost their lives in today’s tragic crash,” he wrote in a tweet.

The cause of the crash remains under investigation.

Police didn’t release the names of those who were killed pending the notification of next of kin.

(AP)