(Newser) – Oil spilled into the Mississippi River yesterday when a barge carrying 80,000 gallons of it hit a railroad bridge in Vicksburg, Miss., the AP reports. Investigators don't know how much oil spilled, but a sheen was reported as far as three miles downriver. A second barge owned by the same company was also damaged, and the waterway was closed for miles, but authorities don't think the Gulf of Mexico—more than 340 river miles to the south—is at risk.

"Investigators are still trying to figure out what happened," says a Coast Guard spokesperson, and authorities are still trying to find the source of the leak. The second vessel does not appear to be leaking; it's not clear whether it hit the first or whether it also hit the bridge. US Environmental Services is working to contain the oil with booms and eventually collect it, but the Coast Guard doesn't know how long the river will be closed in the area. (Read more oil spill stories.)

