HOUSTON (REUTERS) - Torrential rains have killed at least nine people in Texas and Oklahoma, including a homecoming queen returning from her school prom.
In Houston, floods turned streets into rivers and led to about 1,000 calls for help in the fourth-most populous US city, officials said on Tuesday.
The death toll is set to rise with numerous people missing in Texas after the storms slammed the states during the Memorial Day weekend, causing record floods that destroyed hundreds of homes and swept away bridges.
Among the dead was Alyssa Ramirez, 18, who was driving home to Devine, Texas from her high school prom in San Antonio when she was stranded in high water, dialling for help before she was overwhelmed, relatives told local news stations.
She did the right things," her aunt, Roberta Ramirez, told CNN, of her niece, a star tennis and volleyball player, cheerleader, and student council president and star athlete on the tennis and volleyball teams. "She called 911. She called her father, but it was just too much and too quick."
Her distraught parents conducted a desperate search for Ramirez on Saturday night, but emergency crews found her body not far from her car after the flood waters receded, her aunt said.
More than 1,000 vehicles were submerged in floods in Houston and people took instead to bicycles, kayak and surfboards to navigate water-covered streets. The Houston Fire Department rescued about 500 people in boats, local media reports said.
President Barack Obama said on Tuesday he had assured Texas Governor Greg Abbott that he could count on help from the federal government as the state recovers from the floods. Abbott has declared a state of disaster in 24 Texas counties.
Abbott said he has deployed the state's National Guard and was worried the death toll could rise.
"We still have countless people who are missing," he told cable news station CNN.
Twelve people are confirmed missing and about another 30 are unaccounted in flooding that hit along the Blanco River in central Texas, county officials said. The missing were from two families whose vacation home was swept off its foundation in Wimberley, a town about 50 km southwest of Austin.
Search dogs and boats were being used to search for the missing. The river rose so quickly and with such force, it caused a flood gauge to break, Hayes County officials said.
There was no damage estimate available for the state, which has a US$1.4 trillion-a-year economy and is the country's main domestic source of energy as well as an agricultural and manufacturing power.
Houston resident Dutch Small, 40, climbed onto the roof of his car when the water came up to his knees inside his vehicle and was eventually rescued by a passing tow truck driver.
"It happened so fast. Every person that died in the flooding, I know what was going through their minds. They didn't measure the threat accurately. They were like me," Small told Reuters.
More bad weather was expected with the National Weather Service issuing a flash flood warning on Tuesday for Houston as a line of thunderstorms moved along the Gulf of Mexico coast toward Florida. It said there was a high chance of more rain and thunderstorms for Texas this week.
More than 170 flights were at airports in Houston and Dallas, some of the nation's busiest, as blocked roads made it difficult for workers to get to their jobs. A sinkhole also closed a runway at the Dallas/Fort Worth International airport.
About 100,000 customers were without power throughout the state on Tuesday morning due to high winds and rising waters that caused power poles to snap.
About 28 cm of rainwater fell in Houston on Monday while parts of Austin were hit by as much as 18 cm. Helicopter crews in both cities pluck people to safety who had been stranded in cars and on top of buildings.