Two people died and three more were missing after floodwaters caused by heavy rain swept through parts of southeastern Texas Thursday night and Friday, officials said. One person drowned off a road in southern Washington County, while a second person was found dead Friday after going missing overnight was determined to have died of a heart attack, Brenham Fire Department spokeswoman Angela Hahan told NBC News. RELATED: Extreme flash flooding swamps southern Texas Brenham crews are still searching for a missing 21-year-old man, Brenham Fire Chief Ricky Boeker told NBC News. The man's truck was found but not the driver. Over 50 roads throughout the county were closed as more than 20 inches of water flooded the area. Meanwhile, Travis County officials were searching for two residents and had rescued others from rooftops by helicopter, Travis County Emergency Services said. A person called the sheriff's office at 1 a.m. and reported seeing a person hanging on to a pole, surrounded by floodwaters, and said a person and a pick-up truck were swept away by flooding, the county said. Up to 9 inches of rain fell in parts of Travis County overnight, emergency services spokeswoman Lisa Block Told the Associated Press. The torrential downpour was part of severe weather that pummeled the nation's middle Thursday evening, with tornadoes reported in Kansas and Texas. More than 12 million people in the Plains were under flash flood watches Friday, and 1.4 million are under flash flood warnings, said TODAY's Al Roker. Southern parts of the state got an additional 2 inches of rain Friday, according to NBC Dallas-Fort Worth. "Flooding will continue to be a problem probably on into tomorrow and possibly Sunday morning as those floodwaters finally start to recede," Roker said. The rain will swell creeks and rivers that are already bloated from punishing overnight flood totals. Brenham Municipal Airport, 90 miles east of Austin, received the most at 16.84 inches. RELATED: 14 million at risk as thunderstorms threaten Plains, Midwest and South Up to 15 inches of rain fell in parts of southeastern Texas. In Bastrop County, which got about 3 inches of rain per hour, a disaster declaration was issued after about 100 homes were damaged, according to Weather.com. Nearby, in Austin, the Austin Fire Department reported 600 weather-related calls in less than 24 hours. The department rescued 13 people trapped in vehicles and homes by the rising waters. Earlier on Thursday, the National Weather Service confirmed a tornado hit southeast of St. George, Kansas, around 2:05 p.m. local time (3:05 p.m. EST) moving at 30 mph. Another tornado was confirmed between Wamego and Louisville, Kansas. Meanwhile, in Jefferson County, Kansas, baseball-sized hail from two storms fell, said Dr. Greg Forbes, a severe weather expert at the Weather Channel. Over in Kentucky, due to a different weather pattern, at least 19 students got trapped inside a cave after a flash flood rushed in Thursday morning. The students and four tour guide waited on higher ground in Hidden River Cave for the water to recede, then exited safely, according to the Kentucky State Police. This story originally appeared on NBCNews.com.