Updated

Texas Gov. Greg Abbott has declared a state of disaster in 18 flood-stricken counties in Central and South Texas on Tuesday, with one death reported so far, officials said.

Abbott noted in his proclamation that severe weather and prolonged flooding that began on Oct. 7 "has caused widespread and severe property damage and threatens loss of life."

“Texas is taking immediate action to respond to the threat of recent severe weather and flooding across the state,” Abbott said in a statement, according to Austin's The Statesman. “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. I thank all our first responders and local officials on the ground in these communities for their efforts to assist fellow Texans during this dangerous event.”

The counties covered by the declaration are Bastrop, Burnet, Colorado, Fayette, Hood, Jim Wells, Kerr, Kimble, La Salle, Live Oak, Llano, Mason, McMullen, Nueces, Real, San Patricio, Travis and Williamson.

A flash flood warning is in effect, and forecasters describe it as a "very dangerous situation."

It's not expected to drop below major flood stage until later Wednesday, with the weather service's Flash Flood Watch in effect for portions south central Texas through Thursday afternoon, according to NWS Austin/San Antonio.

An unidentified body was found near the eastern shore of the rain-swollen Lake Lyndon B. Johnson on Tuesday, officials said.

The lake is situated where the Llano and Colorado rivers meet. The National Weather Service said both rivers are experiencing "major flooding" following several days of rain.

Burnet County Sheriff's Capt. Tom Dillard said there haven't been other reports of deaths or injuries in the county. He also said the body found Tuesday doesn't appear to be that of a person still missing from a flash flood last week in an RV park along the South Llano River, about 90 miles upstream.

The Llano and Colorado rivers meet at Kingsland and the National Weather Service said both were experiencing "major flooding."  (Austin American-Statesman via AP)

Heavy rains continue to swell the Central Texas rivers, sending water over bridges, threatening riverside structures and prompting recommendations for area residents to evacuate.

Evacuations are underway in the cities of Kingsland and Marble Falls, both northwest of Austin.

In addition to the evacuations, several school districts closed for the day and emergency personnel blocked access to more than 150 low-water crossings.

Raging floodwaters bloated the Llano River, overrunning a bridge in Kingsland, about 65 miles northwest of Austin.

The National Weather Service said the river at nearby Llano is expected to crest at near-record levels near 41 feet, which is 18 feet above major flood stage on Tuesday morning.

Last week, four people were swept away in floodwaters along the South Llano River in Junction. The bodies of three were recovered and one person remains missing.

The Associated Press contributed to this report.