Updated at 4:41 p.m. ET

Texas Gov. Greg Abbott is calling the flood damage in the central part of his state "absolutely devastating."

Abbott flew over parts of the Blanco River Monday, a day after storms triggered flooding. The hardest-hit communities were Wimberley and San Marcos. Abbott added 24 counties to the disaster declaration he issued earlier this month to help communities overwhelmed with heavy rains and tornado damage.

The high water forced Peggy Wilborn — and her neighbors — from their homes in Wimberley.

"They've lost everything: their cars, their furniture; everything," Wilborn said. "And it is just amazing."

The weekend flooding killed one person in Texas and two in Oklahoma.

Texas Public Radio's Eileen Pace reports that officials in Hays County between San Antonio and Austin say at least 12 people are missing and more rain is on the way. Here's more from her report for our Newscast unit:

"The National Guard is back at it in Wimberley, flying in choppers to pluck stranded residents from rooftops and islands created by the still-rising Blanco River."

Hays County Emergency Coordinator Ken Bell said the river is flowing at record speeds and is the worst flood in almost a century.

"The flow and height is double its highest level ever, recorded in 1929," he said. "It's the largest flood in the history of this region."

He said 350 houses were ripped off their slabs by the swollen river – another 1,000 homes were damaged.

Eileen adds: "Further south, in Devine Texas, rescuers Sunday found the body of a high school student — swept away by flood waters on the way home from her high school prom Saturday night."

Separately, a tornado along Mexico's border with the U.S. left at least 13 people dead. Among the missing is an infant who was blown out of her mother's arms by the high winds.

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