At least 25 people are dead after a major storm system ripped through the Midwest, the South and the Mid-Atlantic, bringing tornadoes and severe thunderstorms through Saturday night.

The latest fatalities were reported in Tennessee and Delaware.

The sheriff of McNairy County, Tennessee said Saturday evening that the death toll had grown to nine. All victims were in buildings destroyed down to their foundations, he said.

One death was reported in Delaware's Sussex County, where an apparent tornado struck southeast of the small community of Greenwood, said county spokesperson Chip Guy.

It wasn't clear how many people, if any, were injured, but "several structures were damaged," he said.

Officials in Delaware were waiting for another line of severe weather to move through before conducting recovery operations, Guy said. The apparent tornado was part of the same thunderous weather system that struck the Midwest and South overnight.

The National Weather Service was working to confirm the tornado reports by putting people on the ground to assess damage, which can take time.

"We will be surveying damage from likely tornadoes that struck many of our Middle Tennessee counties overnight, including Wayne, Lewis, Marshall, Rutherford, Cannon, and Macon Counties," the weather service field office in Nashville said on Saturday. "Due to the widespread damage, it will take us several days to reach all these areas."

The damage includes downed trees, power lines and "houses with heavy damage" in multiple counties, according to a list of storm reports collected by the agency.

Five of the U.S. deaths are in Cross and Pulaski counties in Arkansas, four are in Boone and Crawford counties in Illinois, three are in Sullivan County, Indiana, one in Pontotac County, Mississippi, one in Madison County, Alabama, and one in Tipton County, Tennessee, according to officials.