Maryland state police are investigating the cause of an accident early yesterday near Havre de Grace that left one woman dead, another in critical condition and a truck driver in intensive care.

The driver of the 18-wheeler, traveling north on Rte. 155, veered off the road just before 2 a.m. and hit a guardrail and a sign support. The driver was thrown 10 feet from the cab upon impact. One of two women in the cab of the truck, apparently hitchhikers picked up by the truck driver, was killed, said Trooper Nicolas Paros.

The other woman was trapped next to the dead woman until a rescue squad equipped with three 40-ton tow trucks was able to pull her out about six hours later. She was taken to the University Hospital shock trauma unit in Baltimore.

Police said they found marijuana and a handgun in the wreckage, but have not yet pressed charges in connection with the crash.

The truck driver was identified as Michael W. Muphree, 26, of Higden, Ark., said Sgt. Francis Friedel. The women's ages are estimated to be 19 to 25.

Muphree was in fair condition at Francis Scott Key Medical Center's intensive care unit, suffering from cuts and bruises, according to a hospital spokeswoman.