A crash involving multiple vehicles slowed traffic to a crawl across the Chesapeake Bay Bridge’s westbound lanes for about two hours during the July 4 holiday.

All westbound lanes were reopened to traffic after 2 p.m., though Maryland Transportation Authority officials warned motorists to expect continued delays in both directions.

MDTA police officers assigned to the Bay Bridge responded shortly after 11:40 a.m. to the westbound span for a crash involving a passenger vehicle and a tractor trailer. The westbound span was in two-way operations at the time of the crash, said MDTA spokesman Sgt. Brady McCormick in an email.

Investigators believe the passenger vehicle was traveling in the eastbound lane when the driver swerved the vehicle for unknown reasons into the westbound lanes and crashed into the tractor trailer, McCormick said.

A medevac helicopter landed on the Bay Bridge and took the driver to Shock Trauma in Baltimore with serious injuries. The driver of the tractor trailer was not injured.

The crash briefly closed all westbound lanes of traffic, but one lane reopened around 12:50 p.m. By 1 p.m., live cameras showed a long line of vehicles creeping up the bridge’s single open lane.

The MDTA Police Collision Reconstruction Unit is investigating this crash and are asking anyone with information to call 410-295-8146.