State Police are investigating a tractor-trailer crash that tied up traffic for hours in Concord. Police say the truck rolled onto its side on Interstate 93 yesterday morning, blocking both southbound lanes and spilling about 60 gallons of diesel fuel. No one was injured. Police say it appears the truck was traveling at an unsafe speed as it was trying to exit Interstate 393 and enter 93, which led to the trailer weight shifting and the vehicle rolling over. The southbound lanes of 93 were closed for nearly three hours while the truck was moved and the fuel cleaned up.