A one-car crash on Route 3 northbound in Braintree sent the driver and four passengers to area hospitals Monday night, State Police said. Troopers from the Milton barracks responded to the crash at 7:15 p.m. to find that all five occupants had sustained injuries, the driver’s appearing to be serious, according to an email from Trooper Kenneth Gaetz, a State Police spokesman. The driver and two passengers were taken to Boston Medical Center, while the other two were sent to South Shore Hospital. Gaetz said the cause of the crash was unknown and was under investigation.Jeremy C. Fox can be reached at firstname.lastname@example.org. Follow him on Twitter @jeremycfox.