Jessica Durando, and Greg Toppo

USA TODAY

Authorities said Monday they rescued at least 40 people in the past two days from floodwaters in Fort Bend County near Houston, after at least six people died during a weekend of heavy flooding.

Some rivers and waterways were still rising after torrential rain pounded the region last week. Forecasters say flooding of the Brazos River in parts of Texas will continue through Tuesday, when the river is expected to crest more than three feet above its previous record, the Associated Press reported.

The Austin Fire Department said on its Facebook page Monday that Lake Austin, Lady Bird Lake, and the Colorado River downstream of Longhorn Dam are closed to boaters until Wednesday because of flow from Mansfield Dam floodgates opened by the Lower Colorado River Authority.

"It is necessary to start moving water ASAP; The flooding upstream and the potential for more rain has made this emergent," the department said on Facebook.

Austin Fire Department Division Chief Palmer Buck told the Austin American-Statesman, “The flooding at that amount of water is not conducive to happy paddlers.” Buck said, “On Lake Austin that level of water causes damage to docks and property. The LCRA hasn’t seen this level of operations in a long, long time.”

Elsewhere, authorities confirmed that a tornado touched down Monday near the Nebraska border in Peetz. Colorado State Patrol says the storms caused minor damage as residents were told to take cover. There's no word yet on any injuries, KUSA-TV reported.

Six people died and at least two others were missing Sunday after heavy rains in Texas and Kansas caused severe flooding. In one case near Austin, which received nine inches of rain this week, a vehicle with two people was swept off a flooded roadway.

Most of the deaths took place in rural Washington County, Texas, between Austin and Houston, where more than 16.5 inches of rain fell in some places late last week, the Associated Press reported. The bodies of two other missing motorists were found Saturday in separate parts of the county, authorities said.

NBC News reported that one of the victims, 64-year-old Lela Holland, died Friday when floods washed through her home, according to the Washington County Sheriff's Office. Most of the other victims died when their vehicles were overtaken by high water, according to police, including:

Jimmy Wayne Schaeffer, 49, who was killed when he drove his truck into high water;

Darren Mitchell, 21, a National Guardsman, whose vehicle was swept off the road by floods;

Pyarali Rajebhi Umatiya, 59, who was killed after his vehicle stalled in high water.

Two people in Travis County, Texas, were swept away in floodwaters Friday, County Emergency Services spokeswoman Lisa Block told NBC News. A witness reported one person was holding onto a pole and was ripped away by the waters, while firefighters saw another person get swept away in a vehicle, Block said.

Follow Jessica Durando on Twitter: @JessicaDurando