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Austin American-Statesman, Jay Janner, Associated Press
Tex Toler watches the Llano River rise in Llano, Texas, on Friday, May 29, 2015, after another round of heavy rains. Officials are closely monitoring the levels of rivers in Texas engorged by the deluge of last weekend.

HOUSTON — Floodwaters submerged highways and threatened homes Friday in Texas as another round of heavy rain added to the damage inflicted by storms that have killed at least 21 people and left 14 missing.

The line of thunderstorms that stalled over Dallas dropped as much as 7 more inches overnight. That rainfall contributed to another death early Friday, when firefighters in a Dallas suburb said a man drowned in his truck after it was swept into a culvert.

The rain also seeped into homes and stranded hundreds of drivers, many of whom lingered along highways that were nearly gridlocked from the high water and abandoned vehicles.

Fire rescue crews responded to about 260 calls that included trapped vehicles and accidents, authorities said.

Exacerbating the problem for first-responders are people who have been going around barricades to take pictures of the floodwaters, said Dallas County Judge Clay Jenkins. He said those people are endangering themselves and stretching thin the first responders' resources.

"Floodwaters are never safe to play around, take a picture around, walk around," Jenkins said. "We don't need any more loss of life."

Jenkins also said he is considering issuing evacuation orders for Dallas-area neighborhoods depending on the latest flood projections.

The Colorado River in Wharton and the Brazos and San Jacinto rivers near Houston were the main focus of concern as floodwaters moved from North and Central Texas downstream toward the Gulf of Mexico.

Teams continued to search through debris piles along rivers. Bodies found on Thursday raised the confirmed death toll to at least 25, including storm victims from Oklahoma.

The Brazos River, which had been receding, rose above flood stage again Friday in Parker County, west of Fort Worth, and was expected to climb higher with the planned opening of the flood gates at Possum Kingdom Lake upstream. People in about 250 homes near the river were asked to voluntarily evacuate.

With the water moving rapidly down the river, serious flooding was expected in the downstream communities of Simonton and Thompsons. Fort Bend County Sheriff Troy Nehls said some residents of Simonton had already been asked to leave.

Forecasters said the Colorado River at Wharton could crest on Saturday, causing major flooding in the community 60 miles southwest of Houston. Voluntary evacuations were underway in the city's low-lying west side.

Emergency teams rescued a dozen people from flooded homes and stranded vehicles late Thursday in Johnson County south of Dallas.

By early Friday, crews had retrieved the 21 occupants of a houseboat that went adrift in Lake Travis in Austin.

This week's record rainfall in Texas eased the state's drought and swelled rivers and lakes to the point that they may not return to normal levels until July.

Just weeks ago, much of the state was parched with varying levels of drought. But the same drenching rainfall that paralyzed parts of Houston and swept away a vacation home with eight people inside also offered relief from a long dry spell.

Many cities were still in danger of flooding as heavy rain from earlier in the week poured downstream, pushing rivers over their banks.

"There's so much water in Texas and Oklahoma that it's going to take quite a while for those rivers to recede," said Mark Wiley, a National Weather Service meteorologist in Fort Worth, Texas.

If normal amounts of precipitation return, rivers will probably drop to average levels by the Fourth of July, he said.

"Six months ago, we were dying for this stuff," he said. "And now we're saying, 'Please, please stop.'"

Lozano reported from Houston and Robbins from Wimberley.

Associated Press journalists David Warren, Jamie Stengle and Terry Wallace in Dallas; John L. Mone in Wimberley; and Joshua Replogle in Houston contributed to this report.

Follow Juan A. Lozano on Twitter at www.twitter.com/juanlozano70 .