There are still no estimates of when the vital shipping channel linking New Orleans' port with grain elevators, refineries, coal terminals and other commercial facilities upriver will reopen, the Coast Guard said.

Grain movements had not been significantly disrupted as of Thursday, and big refineries upstream were relying on pipelines to feed their units.

About 90,000 feet of protective floating barriers called booms have been deployed, up from half that Wednesday, and skimmers and vacuum trucks have been brought in to contain the damaging scrim of oil, the Coast Guard said.

The accident happened early Wednesday in New Orleans, near Mile 99, when the chemical tanker Tintomara split an American Commercial Lines barge in half, dumping 420,000 gallons of No. 6 fuel oil from the barge into the river.

As the spill spread down the river, the Coast Guard closed more and more of it to traffic Wednesday, extending the shutdown from Mile 97 to Mile 0 - where the river meets the Gulf - by Thursday.

No wildlife impact had been reported yet, but the Louisiana Department of Environmental Quality was monitoring, spokesman Rodney Mallett said.

"It's in the middle of the river," Mallett said. "As it gets on the bank or happens to get over the banks into sensitive habitat, then that's something that we'll have to look at."

Seven drinking water intakes on the river were closed and residents on the West Bank of the river were being urged to conserve water being taken from storage pending restart of affected purification plants.

New Orleans' water supply appeared to be safe. The New Orleans suburb of Gretna switched to the Jefferson Parish water system, and Plaquemines Parish downriver of the accident, requested delivery of water from outside, state officials said.

The tanker and the floating halves of the barge were still being held near the site of the accident, but salvage operations on the vessels were expected to begin Thursday, the spokesman said.

Three refineries were located in the area of the spill along with two major coal-loading terminals. There were no reports of impacts on the refineries. Impacts on the coal-loading terminals were not yet available.

The refineries are operated by ConocoPhillips, Murphy Oil and Chalmette Refining LLC, a joint venture between Exxon Mobil and Venezuelan state oil company PDVSA.

"We get most of our crude via pipeline, so that means that we can operate without issues for a couple of days," said ConocoPhillips spokesman Bill Graham.

The Coast Guard continued to investigate a report that the crew of the tugboat Mel Oliver, pushing the barge involved in the collision, was not properly licensed, a spokesman said. (Additional reporting by Janet McGurty in New York, editing by Chris Baltimore and Marguerita Choy)