At least 16 tornadoes were reported in six states overnight into Tuesday morning.
The twisters were reported in Iowa, Nebraska, Kansas, Oklahoma, Tennessee and South Dakota.
The most destructive storm appeared to have been in Barnsdall, Oklahoma, north of Tulsa, where major damage was reported.
In addition to tornadoes, 4-inch hail, about the size of a softball, was reported in Kansas.
A tornado watch had been issued Tuesday morning for parts of Missouri — including St. Louis — and Illinois. That watch was to be in effect until 8 a.m. local time.
The tornado watch in Arkansas was also extended to 5 a.m. local time.
