State Police are investigating a tractor-trailer accident that happened on I-85 South in Dinwiddie. Police say the tractor-trailer overturned at mile marker 42 around 4:15 a.m. Wednesday. The truck was carrying frozen fish, which it spilled onto the roadway and into the median along the side of the interstate. Cleanup took several hours, during which time the left lane of I-85 South was shut down. No one was injured in the crash.