The parents of 11-year-old triplets who were in a school bus crash in February that killed one of the children are suing the bus and trucking companies involved in the accident.

Anthony and Susan Tezsla say the crash, in which a dump truck struck the school bus at an intersection in Chesterfield Township, resulted from negligence on the part of the companies, GST Transport and Herman's Trucking, and their drivers.

The Tezslas' three daughters were among about 25 elementary school students on the bus.

The accident also severely injured the two other Tezsla sisters and 11-year-old Jonathan Zdybel.

State police cited both drivers for offenses, including failing to yield and not properly securing a load. The trucking company was also cited for not properly maintaining the truck brakes and for overloading the vehicle.

"It was a preventable tragedy," said Dion G. Rassias, the lawyer representing the Tezslas. "It's impossible to quantify the loss [the family] have suffered."

The crash remains under investigation by the National Transportation Safety Board.

On Thursday, the Burlington County Prosecutor's Office released the findings of toxicology tests performed on the bus and truck drivers.

Neither Michael Caporale, 38, the truck driver, nor John Tieman, 66, who was driving the school bus, was found to be under the influence of alcohol or drugs that would have impaired their ability to drive.