BILLINGS, Mont. (AP) — Montana authorities monitored downstream water supplies for contamination Tuesday after a truck crash spilled about 7,000 gallons of a chemical salt used to deice roads into a Yellowstone River tributary near the Wyoming border.

The estimated volume of magnesium chloride spilled was up 2,000 gallons from initial reports. The increase came as authorities gained a better grasp on the scope of the accident after crews pulled most of the wreckage from the Clarks Fork of the Yellowstone.