U.S. officials say 14 people have been killed by a powerful storm in the southeastern state of Florida. In Miami, VOA's Brian Wagner reports, the storm generated at least one tornado that destroyed homes and vehicles in several communities.

The storm, with heavy rain and strong wind hit overnight, when many people were sleeping. Witnesses said they were awakened by the sound of intense winds and crunching noises outside their homes. Because of the storm's timing, many said they had little chance to evacuate their homes and move to shelters.

The storm flattened scores of homes and buildings, and it overturned tractor- trailer trucks across the region. Officials said rescue workers were picking through debris to reach those killed or injured.

Florida Governor Charlie Crist declared a state of emergency for the affected areas. And he said state officials were working to assist the survivors.

"It's important to stay in touch as much as you can," he said. "We realize that some people are without power, we understand it's about 20,000 households without power. Hopefully, a lot of people have radios and can stay in touch."

Weather experts said they were still studying the storm to understand what happened. State meteorologist Ben Nelson said they have identified the formation of one tornado, and may confirm others.

"We had one storm within this overall line," he said. "We call those supercells. And that was a rotating thunderstorm that moved onshore, and it started to produce the tornado once it got over to Sumter county."

Officials compared the latest incident to a series of tornadoes in February of 1998, which killed more than 40 people in Florida. Experts said the 1998 storms were partly caused by the cycle of warm water temperatures in the Pacific Ocean - a phenomenon called El Nino. They say El Nino can affect weather patterns thousands of kilometers away and make normally occurring storms much more intense.

Last month, British meteorologists said 2007 will likely be one of the hottest years on record because of El Nino and global warming patterns. Experts say warmer temperatures can spark weather disasters around the world, such as droughts and flooding.

A new report by the Intergovernmental Panel on Climate Change says global warming also produces stronger hurricanes, especially in the Atlantic Ocean.