A tornado seen north of Chickasha, Oklahoma lowers to the ground on May 6, 2015. [Photo/IC]

OKLAHOMA CITY - Thunderstorm and flash flood warnings were issued for several Great Plains states on Thursday, a day after a series of tornadoes touched down in Oklahoma, causing one death, injuring 12 and flattening buildings.

One woman who sought safety in her home's storm shelter died when it flooded in Wednesday night's storms, Oklahoma police said.

The weather system battered a region from Texas to Nebraska and spawned dozens of reported tornadoes on Wednesday.

Large parts of Oklahoma, Kansas and North Texas were under flash flood and severe thunderstorm watches on Thursday. A tornado warning was issued for the area around the North Texas town of Jacksboro, the National Weather Service said.

Six people from a mobile-home park damaged by a tornado southwest of Oklahoma City were taken to a hospital in the region, including an 80-year-old woman in critical condition with hip injuries, hospital spokeswoman Brooke Cayot said.

Thousands of homes and business in Oklahoma were without power on Thursday morning, the Oklahoma Corporation Commission said.