NEW ORLEANS — Officials in charge of the cleanup of a massive oil spill now approaching three Gulf Coast states said Saturday that a new technique in battling the leaks 5,000 feet beneath the sea showed promise.

Among the various weapons employed against the gushing crude has been the distribution of chemical dispersants on the water’s surface to break down the oil. The new approach involves the deployment of the dispersants underwater, near the source of the leaks. Officials said that in two tests, it appeared to be keeping crude oil from rising to the surface and that the procedure might be used more frequently once evaluations of its impact on the deepwater ecology were completed.

Those experiments at the wellhead of the collapsed Deepwater Horizon oil rig were just one sign of the frantic efforts to contain the roughly 210,000 gallons a day still leaking from the wreckage 11 days after the rig exploded and sank.

Homeland Security Secretary Janet Napolitano announced that she was changing the federal leadership of the oil spill operations. Adm. Thad W. Allen, the commandant of the Coast Guard, took over from Rear Adm. Mary E. Landry. In his first daily briefing, Admiral Allen emphasized that capping the well was his first priority.

“Estimates are useful, but we are planning far beyond that, he said.” It doesn’t really matter, he said, whether it is 1,000 barrels or 5,000 barrels a day that are leaking, he said.

Asked whether the slick was affecting shipping lanes and other offshore drilling operations, Admiral Allen said that disruptions had been minimal.

The tenor on shore among local residents was increasingly angry, with criticism directed at federal officials, whom they said should have responded more quickly after the rig exploded April 20. Some said that not enough booms had been placed in the area, and fishermen noted the growing public concern over contaminated seafood, saying such worries were premature.

Doug Helton, a fisheries biologist who coordinates oil spill responses for the National Oceanic and Atmospheric Administration, said Saturday that more than 600,000 feet of boom had been deployed or was being readied for deployment. But he acknowledged there was just not enough to cover the vast shoreline.

Only six of the 32 oyster beds on the east side of the Mississippi River have been closed, and the oil is still 70 or 80 miles away, according to Mike Voisin, chairman of the Louisiana Oyster Task Force.

“We want people to know there is not tainted seafood right now,” said Harlon Pearce, chairman of the Louisiana Seafood Promotion and Marketing Board and owner of Harlon’s LA Fish & Seafood. “Everything we’re doing is precautionary.”

Gov. Bobby Jindal of Louisiana said at a news conference that he would meet soon with leaders from coastal parishes to develop local contingency plans. He called on BP, the company responsible for the cleanup, to pay for the plans and for the Coast Guard to approve them, arguing that local officials’ perspectives would prove critical in the emergency response.

“This isn’t just about our coast,” he said. “It’s about our way of life in Louisiana — our shrimpers, our fishermen.”