Floodwaters deepened across much of Texas on Tuesday as storms dumped almost another foot of rain on the Houston area, stranding hundreds of motorists and inundating the famously congested highways that serve the nation's fourth-largest city.

At least 19 people have died — 12 in Texas and another 7 in Oklahoma — in the severe storms. Among them were a firefighter in Claremore, Oklahoma, who died during a water rescue, and a woman who died after a tornado struck Bryan County, Oklahoma.

Meanwhile, 14 people are still missing in Texas, including a group that disappeared after a vacation home was swept down the river and slammed into a bridge in the Hay's County town of Wimberley, officials said.

More rain is expected in the Southern Plains into Wednesday, unwelcomed news for flood-weary Texas and Oklahoma, according to The Weather Channel.

Footage shows towering flames in San Francisco as crews battle a fire caused by a gas explosion.

The floodwaters 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.

"Given the magnitude and how quickly it happened, in such a short period of time, I've never seen this before," said Rick Flanagan, Houston's emergency management coordinator.

The flooding closed several highways, and the ones that stayed open became a gridlocked mess.

Interstate 45 near downtown was backed up for miles on Tuesday morning, and a handful of motorists traveled the wrong way on the highway to retreat from high water.

The 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.

Footage shows towering flames in San Francisco as crews battle a fire caused by a gas explosion.

The National Weather Service in Fort Worth warned residents of northwestern Ellis County about a possible dam breach that could cause flooding Wednesday morning.

Grand Prairie Fire Department Det. Lyle R. Gensler said, if breached, the dam on Padera Lake could cause nearly 20 feet of water to spill across roads.

In the Heights neighborhood about 5 miles from downtown, groups of people roamed the streets after escaping their stalled cars, and police cruisers blocked some dangerous roads.

Some motorists were stuck on I-45 all night, sleeping in their cars until the backup was cleared about 8 a.m.

Floods in Houston and central Texas Monday night left fans at the Rockets game stranded, turned highways into rivers and even filled parking garages with several feet of water. See videos posted on social media of the weather and its aftermath.

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.

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

Footage shows towering flames in San Francisco as crews battle a fire caused by a gas explosion.

Officials in Hays County, about 35 miles southwest of Austin, said 30 people who had been reported as missing were accounted for by mid-afternoon Tuesday.

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.

Some of the worst flooding in Texas was in Wimberley, a popular tourist town along the Blanco River. That's where the vacation home was swept away, after the river rose 28 feet in an hour and a half, NBC News reported.

The "search component" of the mission ended Monday night, meaning no more survivors were expected to be found, said Trey Hatt, a spokesman for the Hays County Emergency Operations Center.

One person who was rescued from the home told emergency workers that the other 12 inside were all connected to two families. Young children were among those believed to be missing.

But by early Tuesday, Hays County spokeswoman Laureen Chernow acknowledged discrepancies concerning exactly how many people were in the home.

"We don't have that certainty," Chernow said.

[NATL-DFW] Record Rains Spawn Epic Floods in Texas

Eight of the missing were friends and family who had gathered for the holiday, said Kristi Wyatt, a spokeswoman for the City of San Marcos. She said three more were members of another family in a separate situation. An unrelated person was also missing, Wyatt said.

The Blanco crested above 40 feet — more than triple its flood stage of 13 feet. The river swamped Interstate 35 and closed parts of the busy north-south highway. Rescuers used pontoon boats and a helicopter to pull people out.

Hundreds of trees along the Blanco were uprooted or snapped, and they collected in piles of debris up to 20 feet high.

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 Oklahoma Department of Emergency Management also reported four fatalities between Saturday and Monday after severe flooding and reports of tornadoes.

In Ciudad Acuna, Mayor Evaristo Perez Rivera said 300 people were treated at local hospitals after the twister, and up to 200 homes had been completely destroyed in the city of 125,000 across from Del Rio, Texas.

Thirteen people were confirmed dead — 10 adults and four infants, including one that was ripped from its mother's arms by the storm.