Jamaicans snapped up emergency supplies as Hurricane Dean bore down on their Caribbean island, threatening to become a rare Category 5 storm. Jamaicans snapped up emergency supplies as Hurricane Dean bore down on their Caribbean island Saturday (August 18), threatening to become a rare Category 5 storm when it later nears Mexico's Yucatan and the oil rigs of the Gulf of Mexico. The first hurricane of what is expected to be an above-average 2007 Atlantic storm season has already pounded the eastern Caribbean, where it killed at least three people. It was blamed for three more deaths on Saturday as millions went on alert in some of the most populous areas of the Caribbean including Haiti, the Dominican Republic, Cuba and all of mountainous Jamaica. With sustained winds of 150 mph (240 km per hour), Dean was a Category 4 storm, the second-highest level on the five-step Saffir-Simpson scale. It was expected to smash into Jamaica on Sunday (August 19). It could become a Category 5 storm within two days, with sustained winds of more than 155 mph (250 kph). Just before 5 p.m. EDT (2100 GMT), Dean was located 455 miles (735 km) east-southeast of Kingston and about 165 miles (270 km) south of Santo Domingo. It was moving west-northwest at 18 mph (30 kph), the U.S. National Hurricane Center said. Jamaica's government urged people to flee low-lying and landslide-prone areas, buses were marshalled to transport evacuees and police and troops were put on alert. Lines formed at gas stations and supermarket aisles were crammed as shoppers bought batteries, flashlights, canned tuna, rice and bottled water. The latest computer models showed Dean hitting the northern Yucatan Peninsula on Tuesday (August 21) before emerging in the Gulf, where it could go through the Cantarell Complex of Mexican oil fields, one of the world's most productive. Most models had the storm hitting north Mexico after that, but one took it ashore in south Texas.