The system is forecast to reach hurricane strength near the middle of the week before it reaches the northwestern Gulf Coast.

U.S. Gulf of Mexico oil producers on Thursday were conducting safety checks and preparing to restart some output after Hurricane Francine disrupted operations, while a Louisiana oil refinery ramped up production and export ports reopened.

Tropical Storm Francine started strengthening in the Gulf of Mexico ahead of an expected hurricane strike on Louisiana and parts of the western Gulf Coast by midweek.

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.