The U.S. Coast Guard has closed the river from mile marker 97 to the Gulf of Mexico as crews begin cleanup efforts. Meanwhile, at least 90 deep-water vessels remained stalled by the thick, smelly sheen, with costs mounting during the closure which could last for days or even weeks, The New Orleans Times-Picayune reported Thursday.

"As the spill runs south, more traffic will be able to slowly move on," because it will be possible for the Coast Guard to open more locks, said Coast Guard spokeswoman Jaclyn Young.

The oil spill occurred early Wednesday when a 600-foot Liberian tanker collided with a barge carrying 400,000 gallons of thick, marine oil. The barge was split in half, sending nearly all of its contents into the river. The barge reportedly was being pulled by the tugboat Mel Oliver, which had no appropriately licensed personnel on board at the time of the incident, the newspaper said.