When a bridge over the Yellowstone River collapsed as a train passed over it in Montana, rail cars carrying hot asphalt and molten sulfur fell into the river.

Both hazardous materials quickly solidify when mixed with water, according to news reports, and rail officials suggest the material will not travel far from the accident site.

Watch video showing the collapsed bridge (link may require registration)

What danger the spilled cargo poses to irrigation and to residents dependent upon the river for drinking water is yet unknown, but monitoring of the river is ongoing as removal of the railway cars continues.

Monitoring of the air is also ongoing, but no toxic gases have been reported, according to news reports.

The bridge collapse also cut off high-speed internet service when a fiber-optic cable was damaged.

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