FELIPE CARRILLO PUERTO, Mexico - Hurricane Dean slammed into the Caribbean coast of Mexico today as a roaring Category 5 hurricane, the most intense Atlantic storm to make landfall in two decades. It lashed ancient Mayan ruins and headed for the modern oil installations of the Yucatan Peninsula.

Dean's path was a stroke of luck for Mexico: It made landfall in a sparsely populated coastline that had already been evacuated, skirting most of the major tourist resorts. It weakened within hours to a Category 3 storm, with maximum sustained winds of 125 mph.

The eye of the storm hit land near Majahual, a port popular with cruise liners, and it was racing across the Yucatan Peninsula toward an entry this afternoon into the Bay of Campeche, where the state oil company evacuated the oil rigs that produce most of Mexico's oil.

In the largely Mayan town of Felipe Carrillo Puerto, at one point about 30 miles from the center of the storm, people stared from their porches at broken tree limbs and electrical cables crisscrossing the streets, some of which were flooded with ankle-deep water.

Tin roofing ripped from houses clunked hollowly as it bounced in the wind whistling through town.

“We began to feel the strong winds about 2 in the morning and you could hear that the trees were breaking and some tin roofs were coming off,” said Miguel Colli, a 36-year-old store employee. “Everyone holed up in their houses. Thank God that the worst is over.”

With the storm still screaming, there were no immediate reports of deaths, injuries or major damage, Quintana Roo Gov. Felix Gonzalez told Mexico's Televisa network, though officials had not been able to survey the area. In the Quintana Roo state capital, Chetumal, the storm downed trees and sent sheets of metal flying through the air.

At landfall, Dean had sustained winds near 165 mph and gusts that reached 200 mph - faster than the takeoff speed of many passenger jets. It was moving west-northwest near 20 mph across the Yucatan Peninsula.

The hurricane killed at least 12 people across the Caribbean, picked up strength after brushing Jamaica and the Cayman Islands and became a monstrous Category 5 hurricane Monday. Sections of the Jamaican capital and the island's east suffered severe damage in the storm, and the country postponed Aug. 27 general elections.

Only three Category 5 storms, capable of catastrophic damage, have hit the U.S. since 1935. Dean is the first Category 5 to make landfall in the Atlantic region since Hurricane Andrew hit south Florida in 1992.

Thousands of tourists fled the beaches of the Mayan Riviera. Though expected to escape a direct hit, Cancun still could face destructive winds.

“There's a lot of noisy wind now with this creature all over us,” state civil protection official Francisco de la Cruz said from his offices in Chetumal.

The hurricane center said Dean could gain power as it crosses the Bay of Campeche and would likely be a major hurricane when it makes landfall a second time on Wednesday. The storm's track would carry it into the central Mexican coast about 400 miles south of the Texas border.

“We often see that when a storm weakens, people let down their guard completely. You shouldn't do that,” said Jamie Rhome, a hurricane specialist. “This storm probably won't become a Category 5 again, but it will still be powerful.”

At 4 a.m. PDT, Dean's eye was over the Yucatan Peninsula, 40 miles northwest of Chetumal.

Meteorologists said a storm surge of 12 to 18 feet was possible at the storm's center, which could push sea water deep inland. Heavy rains threatened to inundate the swampy region.

Petroleos Mexicanos evacuated all 18,000 offshore workers and shut down production rigs on the Bay of Campeche - resulting in a production loss of 2.7 million barrels of oil and 2.6 billion cubic feet of natural gas a day.

Today, Dean threatened the Yucatan's most vulnerable population - the Mayan people - many of whom have seen little of the riches from oil or tourism, and still live in traditional wooden slat huts in small settlements all over this low-lying area.

President Felipe Calderon said he would cut short a trip to Canada where he is meeting with President Bush and Canadian Prime Minister Stephen Harper, and travel today to the areas where the hurricane was expected to hit.

Trees fell and debris flew through the air in Corozal on Belize's northern border with Mexico. The government had evacuated Caye Caulker and Ambergris Caye - both popular with U.S. tourists - and ordered a dusk-to-dawn curfew from Belize City to the Mexican border.

Authorities evacuated Belize City's three hospitals and were moving high-risk patients inland to the nation's capital, Belmopan, founded after 1961's Hurricane Hattie devastated Belize City.

Mayor Zenaida Moya urged residents to leave Belize City.

At the southern tip of Texas, sandbags were distributed in the resort town of South Padre Island. Residents were urged to evacuate.

The crew of the U.S. space shuttle Endeavour prepared to land a day early today because of the threat NASA had once feared Hurricane Dean would pose to Mission Control in Houston.

In Mexico during the past three days, officials put more than 50,000 people on flights leaving various parts of the Yucatan peninsula, the federal Communications and Transportation Department said in a statement.

Cancun, well north of Dean's landfall, saw strong winds since the storm swirled over 75,000 square miles, about the size of Nebraska.

Cancun's tourist strip is still marked with cranes used to repair the damage from 2005's Hurricane Wilma, which caused $3 billion in losses. Dean is expected to be even stronger than Wilma, which stalled over Cancun and pummeled it for a day.

Dean had a minimum central pressure of 906 millibars just before landfall, the third lowest at landfall after the 1935 Labor Day hurricane in the Florida Keys and Hurricane Gilbert, which hit Cancun in 1988.

“A very low pressure indicates a very strong storm,” said Hurricane Center meteorologist Rebecca Waddington.

The worst storm to hit Latin America in modern times was 1998's Hurricane Mitch, which killed nearly 11,000 people and left more than 8,000 missing, most in Honduras and Nicaragua.

- Associated Press writers contributing to this report included John Pain in Miami; Karla Heusner Vernon in Ladyville, Belize; Lisa Adams in Mexico City; and Michael Melia in San Juan, Puerto Rico.