The National Transportation Safety Board (NTSB) has found that a truck driver who smashed into two vehicles on the Bay Bridge in Maryland in July — pushing a car over the guard rail and into the river below — was distracted by lights and sounds behind him at the time of the crash, according to a preliminary report by the safety agency.

The NTSB said the truck driver in the July 19 accident was employed by a Canadian trucking company and was on his first solo trip in the United States.

The driver, 29-year-old Gabor Lovasz, told investigators that just before the accident he looked at the driver-side mirror because of lights and sounds behind him. The driver for Bulk Carriers PEI Limited of Prince Edward Island, Canada, said that when he looked back to the road ahead, traffic was stopped and he was unable to avoid hitting two vehicles in front of him.

The truck hit the back of a car which then continued forward and hit a sport utility vehicle. The car was pushed onto and over the 34-in. barrier wall, falling 27 ft. into the bay, according to the report.

The driver of the car was able to swim to rocks at the base of a bridge support, where she was rescued. The car driver suffered minor injuries and the driver of the SUV was not hurt.

The NTSB decided to look into the accident to determine whether there are any nationwide safety issues involved in the crash, according to a Capital Gazette report. AAA Mid-Atlantic and U.S. Sen. Barbara Mikulski, D-MD, have called for a federal investigation into the Bay Bridge’s safety.

The NTSB investigation is continuing.