McDowell County sheriff's Corporal L.S. Noe says authorities haven't determined how many fish or other aquatic wildlife were affected by the spill.
The spill occurred Wednesday when a tractor-trailer overturned on U.S. 52 in McDowell County. An estimated 7,400 to 7,500 gallons of diesel fuel spilled into the river.
Mark Scott with the state Division of Natural Resources says dead fish were found in the river from Powhattan to Eckman.
Agencies investigate fish kill after diesel fuel spills in river
US - Authorities are investigating a diesel fuel spill that killed fish along a more than 4-mile stretch of the Elkhorn River.