Texan Governor Greg Abbot declared a state of disaster in 18 state counties swamped by severe weather and major flooding on Tuesday.
In a statement, he said: “Texas is taking immediate action to respond to the threat of recent severe weather and flooding across the state.
“We have made available all necessary resources to respond as quickly and effectively as possible to this disaster, and to assist those in harm’s way.“
The Llano River level rose above record levels to 12.61m (39.91ft) in Central Texas because of the flash flooding.
Water currents were so powerful they pulled down the nearly submerged FM 2900 bridge.
At least two people are known to have died.
One body was pulled from the Colorado River in Burnet County while Llano County officials confirmed the discovery of a second body on Tuesday.
Where are the Texas flash floods?
Torrential rain has fallen across central Texas for two days with Llano County being deluged by 30.5cm (12 inches) of water.
Nearby houses were evacuated before becoming flooded.
Kingsland, where the bridge collapsed, sits in Llano County, and is the meeting point between the Llano Rove and Colorado River.
Llano County is located about 65 miles northwest of Austin, the state capital of Texas.
Major flooding in Marble Falls forced people from their homes as massive amounts of water poured over the Starcke Dam, dragging large debris.
Marble Falls, home to more than 7,000 people, spans part of the Texas Highland Lakes in central Texas.
The city is located about 58 miles northwest of Austin and 85 miles north of San Antonio
Where are the flash flood declarations?
The flash flood declarations are in a total of 18 counties.
They are Travis, Williamson, Bastrop, Llano, Burnet, Colorado, Fayette, Hood, Jim Wells, Kerr, Kimble, La Salle, Live Oak, Mason, McMullen, Nueces, Real and San Patricio.
Meteorologist Avery Tomasco warned on Twitter: “We are near the beginning of what could be a long-duration flood event in Central Texas.
“Flooding is already severe, and more rain Thurs & Fri will make it that much worse.”