The westbound lanes of the Bay Bridge reopened at about 2 p.m. Saturday, roughly six hours after a multivehicle crash forced detours and shut down the lanes as police sorted out what happened. Transportation officials said multiple people were taken to hospitals.

At around 3:45 p.m., police said investigators with the Maryland Transportation Authority Police Collision Reconstruction Unit believe 23 vehicles were involved in a “chain-reaction crash on the westbound span” and that approximately 20 more vehicles “were involved in a series of secondary crashes.”

Thirteen people were transported to the hospital. Two of them had serious injuries, and none of had life-threatening injuries. The cause of the crash is under investigation.

The wreck tied up traffic in Annapolis and Kent Island starting around 8 a.m., the Maryland Department of Transportation and Anne Arundel County Police said on X, formerly Twitter. The lanes remained closed through midafternoon, the Department of Transportation said, as tow trucks cleared the vehicles.

Anne Arundel Police said traffic was backed up 1.5 miles approaching the Bay Bridge eastbound span throughout the morning.

Traffic on U.S. 50 Bay Bridge was routed onto the eastbound bridge, with cars switching turns on the span while the westbound bridge remained closed, transportation officials said.

Sgt. Brady McCormick, the public information officer for the Maryland Transportation Authority Police for MDTA, confirmed the crash and lane closures. He couldn’t say how many cars were involved, only that there were multiple. He called the crash “serious.”

In a news release sent later Saturday morning, MDTA stated “multiple patients” have been taken to the hospital and that police are investigating the crash.

The bridge crosses the Chesapeake Bay, connecting Maryland’s Eastern Shore and the metropolitan areas of Baltimore, Annapolis and Washington.

A previous version of this story incorrectly referred to a police agency as the Maryland Department of Transportation Police. It should have been Maryland Transportation Authority.