A leak from an undersea pipeline network in the Gulf of Mexico released nearly 90,000 gallons of crude oil before being discovered and shut down, federal regulators said.

Royal Dutch Shell said it shut down that network after the leak was discovered and identified the source of the leak early Friday. The Coast Guard says the spill released 88,200 gallons of oil before being plugged.

That's a small fraction of what spewed into the Gulf each day during the three-month Deepwater Horizon disaster in 2010, but it has given new fuel to campaigners who want to close off the Gulf to new wells.

"We're calling for no new drilling in the Gulf of Mexico, and this is exactly why," said Anne Rolfes, founder of the environmental group Louisiana Bucket Brigade.

'No release is acceptable.'

Thursday's leak spill left a sheen of oil across roughly 26 square miles of the Gulf, according to the federal Bureau of Safety and Environmental Enforcement, which oversees offshore drilling. A Shell helicopter crew spotted the leak and called it in, the company said in a written statement.

Once discovered, Shell said it cut off the flow of oil from the four wells that feed into its Brutus production platform, located about 165 miles south of New Orleans. A robot submarine identified the leaking line early Friday, and was looking for any additional releases.

"On-water recovery vessels are searching for oil that can be safely recovered via skimming," the company said. Five ships have been called out to work on the spill, it said.

"No release is acceptable, and safety remains our priority as we respond to this incident," Shell said.

In the 2010 disaster, a BP-owned well being drilled into the floor of the Gulf blew out, sinking the drill rig Deepwater Horizon and killing 11 workers. The well released an estimated 134 million gallons of crude before it was capped, and tar balls and larger chunks of weathered oil are still turning up along the Gulf Coast six years later.

"By no means do I think this is another BP," Rolfes said. "But this is a big spill, it's significant, and our part of the world kind of rolls along as if it's not a big deal."

Gulf wells provide about 17 percent of American crude, and the industry provides or supports up to a quarter of a million jobs along the coast, according to industry estimates. But it's facing increasing resistance from activists like Rolfe, one of dozens of protesters who disrupted a federal offshore lease auction at New Orleans' Mercedes-Benz Superdome in March.

The Coast Guard says it's conducing an aerial survey of the spill. And Cynthia Sarthou, executive director of the New Orleans-based Gulf Restoration Network (GRN), said her organization is trying to conduct its own overflight as well.

"People need to acknowledge that when you have oil and gas development off your shores, significant oil spills are a part of life," Sarthou said.

Sarthou said not enough has been done since Deepwater Horizon to tighten offshore safety rules, and GRN is organizing demonstrations at government hearings on new drilling projects across the coast.

"This happens more frequently than people talk about," she said.

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