Tropical Storm Dolly dumped rain over Texas and Mexico Thursday after pummeling the coast as a category two hurricane a day earlier, leaving widespread floods in its wake.

The Gulf of Mexico's first hurricane of the season ripped off rooftops, shattered windows and toppled trees and power lines, but the storm surge did not cause any breach in south Texas levees as some authorities had feared.

By Thursday morning, winds had weakened to 50 miles per hour (80 kilometers per hour) and was expected to downgrade again to a tropical depression later in the day, according to the National Hurricane Center.

No deaths were immediately reported in Texas or Mexico as a result of the storm, though one 17-year-old Texas boy broke several bones when the gusts knocked him out of a seven story building, US media reported.

The storm dumped six to 12 inches of rain (15 to 30 centimeters) and cut power to as many as 100,000 people in south Texas late Wednesday.

Texas Governor Rick Perry declared a disaster situation in 15 counties across the southern portion of the state, deploying hundreds of National Guard troops and other emergency crews, local media said.

Jacqueline Bell, who lives on South Padre Island where Dolly made landfall as a category two hurricane packing 100 mph winds (160 kph) midday Wednesday, told CNN the wind had blasted the roof off her neighbor's home.

"When we heard the first bang, I thought it was one of the air conditioners flying ... and then we went outside and we saw the debris," Bell said.

Thirty-five miles (60 kilometers) to the south, in Matamoros, Mexico, Dolly's winds damaged the city's main water treatment plant, leaving half of the 500,000 inhabitants without drinking water.

The river level in Brownsville, Texas rose steadily but the older levees in the Rio Grande Valley withstood the waters, after some officials had voiced concern that the levees could be overwhelmed.

"Everything is in good shape. We are not experiencing flood conditions in the Rio Grande today," Sally Spener, spokeswoman for the International Boundary and Water Commission, told AFP.

"We do not expect water to be high enough to pose any threat to the levees," she said. "The flooding that they are having is localized street flooding in a lot of communities."

Due to dangers posed by the continuing rain, dangling power lines and high waters in some parts of south Texas, authorities urged residents to limit their activities as much as possible.

"Unless it's life or death," Tony Pena, Hidalgo County emergency management coordinator, urged residents to stay at home, the Houston Chronicle said.

Initial damage estimates from the storm by risk-modeling service provider AIR Worldwide Corporation varied between 300 million and 1.2 billion dollars in the United States, and less than a quarter of those amounts in Mexico.

"The considerable uncertainty in the loss estimates is due to Dolly's slow forward motion, its significant precipitation and the uncertainty in its future track as it makes its way inland," it said in a statement.

The NHC has forecast an especially active 2008 weather season, saying there could be up to nine hurricanes and 12 tropical storms in the Atlantic region. The Atlantic hurricane season runs from June 1 through the end of November.