A truck fire that broke out Saturday on I-93 in Waterford was still under investigation as of last night. A plume of black smoke was visible from a distance beginning at about 4:45 p.m., as crews from Waterford and Concord responded to the scene on I-93 south, a short distance from the I-91 interchange. The vehicle, a 2019 Dodge Ram, was engulfed in flames and later declared a total loss. The Waterford Fire Department extinguished the fire, and it was knocked down at 5:15 p.m., according to the police scanner. The operator, Garett Willis, 28, of Littleton, N.H., was reported to have suffered severe burns, and was transported to NVRH for treatment. Willis’ injuries are not life threatening, police said, and he is in stable condition. I-93 south was cleared for traffic at approximately 6:29 p.m.