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WASHINGTON — The Trump administration on Thursday made public its rollback of a major offshore-drilling safety regulation, significantly weakening an Obama-era rule that was put in place after the 2010 Deepwater Horizon explosion in the Gulf of Mexico, which killed 11 people and sent 4.9 million barrels of oil gushing into the sea, causing the worst oil spill in American history.

Interior Secretary David Bernhardt, a former oil lobbyist who was confirmed by the Senate last month to head the agency that oversees the nation’s public lands and waters, announced the plan Thursday afternoon in Port Fourchon, La., the vast industrial hub that serves as the onshore base for most companies that drill in the Gulf of Mexico.

The oil industry praised the move. Environmental groups warned that the rollbacks could pave the way for similar crises to happen again.

The weakened safety rules come as the Trump administration has also sought to vastly expand offshore drilling in the nation’s waters. Last year the Interior Department proposed opening almost the entire United States coastline to drilling, although Mr. Bernhardt recently said the administration may delay those plans while court challenges are addressed.