More rain has fallen on Houston, threatening to complicate the clean-up after a long holiday weekend of storms and floods that left at least 17 dead and more than a dozen others missing in Texas and Oklahoma.

Storm clouds approaching Texas, 2 October 2014.

Storm clouds approaching Texas, 2 October 2014. Image by Ralph Arvesen / CC BY 2.0

The forecast was for 2 to 3 more inches of rain in the Houston area, a day after flooding triggered by nearly a foot of rain in a matter of hours swamped neighbourhoods and highways and stranded hundreds of motorists.

Crews resumed the search for 11 people missing and presumed dead after the swollen Blanco River surged through the small tourist town of Wimberley, between San Antonio and Austin. Houston mayor Annise Parker said two people whose boat capsized during a rescue effort were also missing.

Authorities, meanwhile, defended their warnings to residents ahead of the weather, which included alerts via phone and in person, but acknowledged the difficulty in reaching tourists and said a messaging system in Houston needs improvements.

In Houston, warnings from the National Weather Service buzzed on mobile phones, but city officials say they have not installed a system that would allow them to alert residents with more targeted warnings.

The city is still working with the Federal Emergency Management Agency to get that system running, said Michael Walter, spokesman for Houston’s Office of Emergency Management.

Floodwaters in Houston affected virtually every part of the city and paralysed some areas. Firefighters carried out more than 500 water rescues, most involving stranded motorists. At least 2,500 vehicles were abandoned by drivers, and up to 700 Houston-area homes were damaged, officials said.

More than 100,000 gallons of sewage spilled yesterday from a flooded-out Houston treatment plant, officials said. They said that the spill was contained and that residents do not have to boil their water, but they should not swim in areas around the plant.

The death toll stood at 13 in Texas and four in Oklahoma.

The deaths in Texas included a man whose body was pulled from the Blanco; a 14-year-old who was found with his dog in a storm drain; a high school student who died on Saturday after her car was caught in high water; and a man whose mobile home was destroyed by a reported tornado.

The drenching rain threatened to linger. National Weather Service forecasts called for a 20 to 40 percent chance of thunderstorms through the rest of the week in Houston, and more storms were also in store for central Texas.

(Press Association)