HOUSTON (Reuters) -Nearly a fifth of crude oil production and 28% of natural gas output in U.S. Gulf of Mexico federal waters remains offline in the aftermath of Hurricane Francine, the U.S. offshore energy regulator said on Sunday.

Francine marched through prime offshore oil and natural gas producing areas and hit Louisiana as a Category 2 hurricane on Wednesday. The storm toppled trees, flooded coastal areas and cut power in four southern states.

Energy producers on Sunday had 338,690 barrels per day of oil production and nearly 515 million cubic feet of natural gas offline in Gulf waters, the Bureau of Safety and Environmental Enforcement estimated from producer reports.

Cumulative offshore production losses due to Francine total 2.16 million barrels of crude oil and 4.635 billion cubic feet of natural gas, according to a Reuters tally of BSEE daily estimates.

There were 37 oil and gas platforms still evacuated on Sunday, about 10% of the Gulf of Mexico total, down from 171 evacuated offshore platforms at peak last week, the offshore regulator said citing reports from producers.