BATH — The investigation into a crash that forced police to close Route 1 in Bath for several hours last week has been hampered by the fact that police have been unable to interview the driver of the car that allegedly caused the accident.

Lt. Stan Cielinsky of the Bath Police Department said the driver, 22-year-old Joseph Boyington and his passenger, 21-year-old Michael Mason, both of Brunswick, had to be hospitalized after the March 19 crash.

Cielinsky said Mason is still a patient at Central Maine Medical Center in Lewiston – his condition was not available today. Boyington, who has been a  patient at Maine Medical Center in Portland, has been discharged, according to a spokesman.

Police said Boyington was behind the wheel of a 2003 Acura when it hit the rear end of a 2008 Lincoln SUV operated by 43-year-old Stephanie Thacker of Brunswick. Thacker and her 11-year-old son, Adam, were not seriously injured.

The crash sent the Acura rolling off Route 1 into a Maine Department of Transportation sign.

The cause of the crash has not been determined. Investigators have said the Acura appears to have been travelling at a high rate of speed. The speed limit in that area of Route 1 near the Congress Avenue overpass is 35 miles per hour.

The results of a toxicology test on Boyington are not available yet, according to Cielinsky.