One person was injured after the semi-truck they were in, left Interstate-40, collided with trees in the median, which led to a fire. Flagstaff Police say the accident happened in the area of the I-17 and I-40 interchange at around 5:15 a.m. Saturday. Witnesses told police the vehicle began swerving on the westbound lanes east of the Flagstaff city limits, just prior to leaving the highway. A Flagstaff Fire crew arrived to quickly put out the fire. The driver, and his pet, were able to escape the wreck. The driver was taken to Flagstaff Medical Center with non-life threatening injuries. The accident is under investigation.