Updated

State wildlife officials say the death toll of whitefish in the Yellowstone River could be much higher than what's already been counted.

Bozeman Daily Chronicle reports (http://bit.ly/2aZtvMn ) that Montana Fish, Wildlife and Parks had counted about 1,000 dead fish as of Monday. But agency spokeswoman Andrea Jones says there could be more than 10,000 dead fish, as some may have sunk to the bottom or been eaten by scavengers.

The mountain whitefish, which is a native species to Montana, have been found dead on both the river's east and west banks.

Officials are still working to determine what's been causing the die-off.

Kristi Ponozzo with the Montana Department of Water Quality says fish samples have been sent to a lab for testing and results are expected in coming weeks.

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Information from: Bozeman Daily Chronicle, http://www.bozemandailychronicle.com