HOUSTON (Reuters) – Oil producers on Monday were evacuating offshore production platforms in the U.S. Gulf of Mexico as the 27th named storm of the season strengthened overnight and is expected to become a hurricane.

BP and Chevron Corp said they were withdrawing staff from U.S. Gulf of Mexico offshore facilities and monitoring Tropical Storm Zeta’s track.

The storm could reach hurricane strength before striking the Yucatan Peninsula at mid-day Monday, and approach the northern Gulf Coast on Wednesday at or near hurricane strength, the U.S. National Hurricane Center said.

Zeta was about 175 miles (285 km) south of Cozumel, Mexico, on Monday morning and moving northwest at nine miles per hour. Mexico’s government issued a hurricane warning for parts of the Yucatan Peninsula.

“With forecasts indicating the storm will move across the Central and/or Northeastern Gulf of Mexico in the next few days, we are taking steps to respond,” BP said in a statement. It pulled oilworkers off its four production platforms in the Gulf.

Chevron said it was withdrawing non-essential staff and its coastal energy plants were monitoring the storm’s track.

U.S. Gulf of Mexico offshore oil production accounts for about 17% of total U.S. crude oil production and 5% of total U.S. dry natural gas production.

If Zeta strikes the U.S. mainland, it would top the record of 10 named storms to make U.S. landfall in one hurricane season that was set only weeks ago by Hurricane Delta.

It has been a challenging year for Gulf of Mexico oil producers, with some companies having to withdraw workers and halt production at least six times from storms churning through the Gulf’s offshore production region.

(Reporting by Gary McWilliams; Editing by Giles Elgood)