Janet McConnaughey

A barge carrying 80,000 gallons of oil hit a railroad bridge in Vicksburg, Miss., on Sunday, spilling light crude into the Mississippi River and closing the waterway for eight miles in each direction, the Coast Guard said. A second barge was damaged.

Investigators did not know how much had spilled, but an oily sheen was reported as far as three miles downriver of Vicksburg after the 1:12 a.m. incident, said Lt. Ryan Gomez of the Coast Guard’s office in Memphis, Tenn.

Authorities were still trying to determine the source of the leak, but it appeared to be coming from one or two tanks located at the stern of the first barge, Gomez said. He said there was no indication that any oil was leaking from the second vessel, and said it was still unclear whether the second barge also hit the bridge or was damaged through a collision with the first.

“Investigators are still trying to figure out what happened,” he said.

The privately owned response-and-remediation company United States Environmental Services was working to contain the oil with booms before collecting it and transferring it to one of the barge’s undamaged tanks, then ultimately to a separate barge, Gomez said. He could not say how long the river would remain closed in the area.

“It’s still considered an active leak,” Gomez said. “We don’t have an estimate or accurate amount of what was released.”

Railroad traffic was allowed to continue after the bridge was found safe for trains, Petty Officer Carlos Vega said.

The oil sheen from Sunday’s incident was unlikely to pose a threat to the Gulf of Mexico, 344 river miles south of Vicksburg.