Efforts to bring oil and gas production back online in the Gulf of Mexico slowed Sunday as Hurricane Ike barreled toward the nation's energy complex, likely to be the second hurricane to slam into the Gulf in as many weeks. Royal Dutch Shell said it would keep staffing at its offshore installations to a minimum as it monitors the storm, which was described as "extremely dangerous" by the National Oceanic and Atmospheric Administration on Sunday.

Other producers were also watching Ike, which was about 90 miles northeast of Cuba and traveling fast. The storm could strike the U.S. coast by midweek.

"Offshore oil and gas operators in the Gulf of Mexico who are re-boarding platforms and rigs and restoring production following Hurricane Gustav are now starting to take precautions for Hurricane Ike," the U.S. Minerals Management Service said on Sunday.

According to the latest storm track, the hurricane could strike any where from Florida to Texas.

Ike is now a Category 4 storm with sustained winds of 135 miles an hour and is creating surges of as much as 18 feet above normal tide levels. Those swells will likely hit portions of the Southeast United States over the next couple days.

More than a quarter of the personnel from the 717 manned platforms in the Gulf of Mexico have been evacuated, and 10 of the 121 Gulf rigs have had staff removed, according to the U.S. Minerals Management Service.

Nearly 80 percent of all oil production in the Gulf, or about 1.3 million barrels per day, has been shut in, according to the MMS. About 70 percent of all natural gas production is off, or about 7.4 billion cubic feet.

Oil and gas producers have been sending workers back to platforms and rigs for the past several days in the wake of Hurricane Gustav, which largely spared the nation's energy complex. Power shortages have continued to hamper the restart of some refineries on the Gulf.

"It's impossible to say how much of that would have come back on line from Hurricane Gustav if another hurricane were not headed for the Gulf," said MMS spokeswoman Caryl Fagot.