VICKSBURG, Miss. — Cleanup crews with booms skimmed oily water from the Mississippi River a day after a barge with more than 80,000 gallons of oil struck a railroad bridge near Vicksburg, spreading a sheen of light crude that kept part of the waterway shut to ship traffic Monday, authorities said.

It remained unclear Monday how much oil had leaked into the river, according to the Coast Guard and Army Corps of Engineers. Petty Officer Third Class Jonathan Lally, a Coast Guard spokesman, said oil was still discharging, but slowly.