Twelve northbound vessels and 12 southbound vessels were waiting to pass Monday, according to Breazeale.
Herman Smith, superintendent of the Vicksburg Bridge Commission of Warren County, said the railroad bridge gets hit about once or twice a year, usually during floods. During the 2011 flood, it was hit five times in two weeks.
The river isn't in flood stage now, Smith said. It was at 33.5 feet Sunday.
Coast Guard spokesman Lt. Ryan Gomez said investigators reported that a towboat or tug was pushing two tank barges when the collision occurred about 1:30 a.m. Sunday.
The second barge was damaged, Gomez said.
Authorities inspected and declared the railroad bridge safe for trains after the collision Sunday. That day, the oily sheen was reported up to three miles downriver from the bridge.
Gomez said crews have laid down a boom and also a secondary boom. They also were using a rotating skimmer device to sweep up oily water in the river.
"They have the boom to contain any crude oil that's leaking out of the barge. They have a secondary boom to corral any crude oil that gets past the first boom," Gomez said. United States Environmental Services, a response-and-remediation company, was working on the booms and collecting the oily water, he said.
He said crews also were in the process of working to transfer the remaining oil.
"They are continuing to try to remove the product from the damaged tank to one of the non-damaged tanks on the same barge," he added. "The ultimate goal is to transfer all of the crude to a different barge."
Gomez said the barge was southbound at the time of the collision, but investigators were still trying to figure out exactly what happened.
The oil sheen was unlikely to pose a threat to the Gulf of Mexico, more than 340 river miles south of Vicksburg.