A four-car accident on Route 5 in Hughesville at midweek injured three people and shut down traffic on one of Charles County's main arteries for about two hours, the Maryland State Police said.

The crash began about 2:45 p.m. Wednesday when John A. Santoiemma Jr., 34, of Lusby slammed into the back of a vehicle driven by Brittany E. Fowler, 21, of Mechanicsville in the left southbound lane of Route 5 just north of Route 231, police said.

The impact of Santoiemma's Monte Carlo sent Fowler's Oldsmobile into the northbound lanes, where she collided head-on with a Ford Escape sport-utility vehicle driven by Suzanne N. Viger, 43, of Frederick, police said.

Debris from the second impact flew into the air and struck a Plymouth Voyager driven by Bebeth A. Gozum, 39, of Oxon Hill, police said. Santoiemma, who police said was at fault in the accident, then drove off the roadway, and his vehicle flipped over in a field.

Police said they found PCP in Santoiemma's car. They said they were awaiting the results of blood tests to determine whether drugs were a factor in the accident.

"They were moving at a constant speed, and he just slammed into the back of her," said Trooper Adam Kolle of the Maryland State Police. He said the investigation was continuing.

Santoiemma was flown to Prince George's Hospital Center with incapacitating injuries, police said, but was in stable condition. Fowler, who was put in a neck brace and had cuts on her legs, was taken to St. Mary's Hospital, Kolle said. Viger suffered bruises from her seat belt, and Gozum was able to drive away uninjured, the officer said.

The accident closed the northbound and southbound lanes of Route 5, and the backup stretched about half a mile, Kolle said. Police were telling motorists to turn around and find other routes.

"Nothing could move," Kolle said.

The accident took place on a narrow and often crowded stretch of Route 5. Law enforcement and transportation officials expect the Hughesville bypass, a $52.6 million project scheduled to open in the summer of 2007, to alleviate congestion along the roadway.