Deadly severe weather over the long holiday weekend tested government alert and evacuation procedures, as officials scrambled to deal with storms and historic flooding that left more than a dozen people dead and a similar number missing.

Crews will resume searches Wednesday for the 11 people who have now been missing for three days in the small tourist town of Wimberley, where the usually calm Blanco River swelled to an ocean-like squall that crested three times above flood stage. In Houston, where nearly a foot of rain submerged roads and stranded hundreds of motorists, Mayor Annise Parker said two people who capsized in a boat that was helping with rescue efforts Tuesday have not been found.

At least 17 people were killed in the Memorial Day weekend storms in Texas and Oklahoma.

Authorities defended their warnings to residents ahead of the weather, which included alerts via phone and in person, but acknowledged challenges with reaching tourists and said a messaging system in Houston is still waiting for improvements.

“Nobody was saying, ‘Get out; get out; get out,'” said Brenda Morton of Wimberley. “We’re pretty trained, so we were calculating. We knew the flood plain. People who were visiting or had summer homes, you have company from out of town, you don’t know. You don’t know when that instant is.”

Morton lives three houses down from a two-story vacation home that authorities say was swept off its 10-foot pylons by a wall of water early Sunday morning with eight people inside, which included three children, ages 6 and 4. The house slammed into a bridge after being carried downstream on the Blanco.

Authorities in surrounding Hays County said warnings included multiple cellphone alerts and calls to landlines. Some received in-person warnings to evacuate, but officials could not say whether those in the washed-away home talked to police.

“Law enforcement made notification along that street. Whether they made contact with somebody at their residence, I can’t say,” Hays County Emergency Management Coordinator Kharley Smith said.

Wimberley, a popular bed-and-breakfast getaway near Austin and surrounded by wine vineyards, thrives on weekends like Memorial Day. Some of the missing had homes in the area, but officials have acknowledged that their electronic alerts may not reach tourists.

“Most definitely, most definitely that will certainly be part of our discussion,” Hays County Commissioner Will Conley said.

In Houston, warnings from the National Weather Service buzzed on mobile phones, but city officials say they haven’t yet installed a system that would allow them to alert residents with more targeted warnings. The city was still working with the Federal Emergency Management Agency to get that framework running, said Michael Walter, spokesman for Houston’s Office of Emergency Management.

Floodwaters in Houston affected virtually every part of the city and paralyzed some areas. Firefighters carried out more than 500 water rescues, most involving stranded motorists. At least 2,500 vehicles were abandoned by drivers seeking higher ground, officials said.

“A number that we don’t know, and we will never know, is the number of lives that have been saved by the effective response of first responders,” Texas Gov. Greg Abbott said in Houston.

Small cars weaved between massive 18-wheelers as other drivers stared at them in disbelief. With no end to the backup in sight, some drivers got off the freeway, only to be held up again by water covering nearby access roads. Some motorists were stuck on I-45 all night, sleeping in their cars until the backup was cleared shortly after sunrise.

NBA fans at the Toyota Center, where the Rockets hosted a Western Conference finals game against Golden State on Monday, were asked with about two minutes left in the game not to leave the arena because of the severe weather.

The game ended before 11 p.m., but about 400 people remained in their seats at 1:30 a.m., choosing to stay in the building rather than brave the flooded roads that awaited them outside.

A spokeswoman for the flood district of Harris County, which includes Houston, said up to 700 homes sustained some level of damage.

Abbott said 46 counties in Texas have state disaster declarations. President Barack Obama has said he expressed condolences to Abbott and anticipates significant requests for federal assistance.

Crews were also searching for victims and assessing damage just across the Texas-Mexico border in Ciudad Acuna, where a tornado killed 13 people Monday.

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 senior who died 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.

(AP)