By Jose Cortazar

CANCUN, Mexico, Aug 18 (Reuters) - Authorities began evacuating residents of the Mexican Caribbean on Saturday and tourists in Cancun cleared supermarkets shelves as the luxury resort braced for its second ferocious hurricane in two years.

Hurricane Dean, which is on the verge of becoming a rare Category 5 storm, was expected to strike the Yucatan Peninsula late on Monday, according to the U.S. National Hurricane Center.

It has already killed at least three people in the Caribbean on its way toward Jamaica and the Gulf of Mexico.

Mexican navy and army officers evacuated 2,500 people from the small island of Holbox and helped fishing communities to shelters on higher ground. Hotel owners and state officials in Cancun were to decide when to move some 40,000 tourists later on Saturday.

"We are not taking any chances with Hurricane Dean," Felix Gonzalez, governor for Cancun's Quintana Roo state, told reporters.

Gulf ports were open on Saturday. State oil company Pemex said its operations in the Gulf of Mexico were normal and it would not take any decisions to evacuate staff until later in the weekend.

Royal Dutch Shell <RDSa.L> said it was removing 300 more support workers from its U.S. Gulf of Mexico facilities on Saturday because of Dean. Shell said it has evacuated about 460 people since the start of the week.

Tourists and locals stocked up on food and water, emptying the shelves at some stores.

"I came to see what I could get, but there's not much left in the supermarket," said Jorge Sanchez, 48, an airport worker shopping at a Wal-Mart store in Cancun.

Cancun is still recovering from Hurricane Wilma, a Category 4 storm on the five-step Saffir-Simpson intensity scale that hit in October 2005 and killed at least seven people.

Wilma howled over Cancun and nearby Cozumel Island for two days, sucking away entire white sand beaches, stranding tens of thousands of tourists and causing hundreds of millions of dollars in damages and lost revenues.

Quintana Roo issued storm alerts on local radio in Spanish, English and the local indigenous language Maya, while Mexico's national rescue service said it had 287 shelters ready across the state.

A Cancun airport official told Reuters that airlines had agreed to cut the number of incoming flights and were prepared to fly out thousands of tourists before the hurricane neared.

AlertNet news is provided by