Security blocks required by the Coast Guard were not placed behind the wheels of a tractor-trailer that rolled off a ferry bound for Long Island Tuesday, killing a Connecticut trucker, according to published reports.

The wedge-shaped blocks, called chocks, should have prevented the truck from rolling, investigators said. Coast Guard regulations specify that vehicles at both ends of the ferry should have their wheels securely chocked while the vessel is underway.

The ferry company, Cross Sound Ferry of New London, was responsible for placing the blocks behind Michael Zuber's truck, which was pulling equipment that pushed its weight to about 100,000 pounds. It was too early to discuss criminal charges, Detective Lt. Jack Fitzpatrick, commanding officer of the Suffolk County Police homicide squad, told The Hartford Courant.

Although Zuber's death has been ruled a drowning, authorities Wednesday were still puzzled about what caused the truck to break through a chain fence at the back of the ferry about 10 a.m. Tuesday. The ferry, traveling from New London, CT, was about three-quarters of a mile from the dock at Orient Point when the accident occurred.

Suffolk County, NY, police divers planned to examine the truck Thursday to determine whether the ignition was in the "on" position, the parking brake was on and what gear the truck was in. The ferry company plans to raise the truck, which lies in about 85 feet of water in a treacherous spot called Plum Gut.