Storm deaths hit 11 in Texas

A boy and his family are carried to safety from flood waters caused by heavy rains in Houston, Texas, on Sunday

HOUSTON, Texas (CNN) -- A weakened Tropical Storm Allison drifted away from Houston on Sunday -- after furiously pounding southeast Texas for five days with torrential rains -- and slowly headed across the Gulf of Mexico for Louisiana.

Eleven people have been confirmed dead in Texas and one in Louisiana since the storm came ashore on Tuesday.

James White, the Harris County, Texas, emergency management coordinator, said that most of the dead had drowned, but that two had died of electrical shock.

Houston authorities expect the number of confirmed deaths to climb as waters recede and rescue crews can reach more areas.

About 12,000 homes or businesses are without power, White said.

VIDEO National guard rescues victims of flooding in the Houston, Texas area (June 10) Play video (QuickTime, Real or Windows Media) Flooding brings Houston, Texas to a standstill, blamed for one death so far. CNN's Donna Kelley reports (June 9) Play video (QuickTime, Real or Windows Media)    IN-DEPTH Hurricanes: How they form and tips on preparing for them     RESOURCES CNN weather forecast for Houston, Texas

On Saturday, President George W. Bush declared a disaster area in 28 counties around Houston, making federal emergency aid available to the region.

"It's unbelievable what's happening here," said Houston Mayor Lee Brown after a helicopter tour of the city. "We have problems all over the city, flooding all over downtown and every other part of the city."

The Coast Guard and National Guard were on duty helping to rescue stranded people and maintain shelters for those who had evacuated their homes.

Tropical storm warnings were discontinued early Sunday as Allison died down, but forecasters warned that the storm could pick up strength again as it chugged across the warm, open water of the Gulf toward southern Louisiana.

Heavy rains in the region -- nearly 11 inches of rain have fallen in the last 30 hours in Houston, and more than 9 inches have drenched Salt Point in southeast Louisiana -- kept flood warnings and watches alive.

Vehicles and homes lay submerged in floodwaters in Houston, Texas, on Sunday

Around Houston, roadways were still flooded and closed down on Sunday -- although the city got a reprieve on Saturday when heavy rains failed to materialize and some of the floodwaters began to recede.

But the threat of more rain on Sunday made it unlikely that all of the roads would reopen soon.

"This is the most disastrous effect on transportation I've seen, even more than the hurricane (Alicia) in the '80s," Brown said. "I-10 looks like a swimming pool for four-wheelers."