Authorities say 5,000 gallons of a chemical used to deice roads spilled into the Clarks Fork River following a semitrailer crash near the Montana-Wyoming border.
    
The Montana Department of Environmental Quality said dozens of fish were killed Monday after two tankers filled with magnesium chloride went into the river and one broke open.
    
Initial reports from authorities incorrectly named another chemical, potassium chloride.
    
Bob Gibson with Montana Fish, Wildlife and Parks says magnesium chloride is designed to dilute quickly, which could lessen the environmental damage.
    
Authorities said public water users downstream of the crash site were notified of the spill. Crews patrolled the banks of the river looking for additional damages.
    
The unidentified driver of the semitrailer, operated by Lynch Trucking of Riverton, Wyo., was cited for careless driving.