Powerful storms and tornadoes sweeping across the nation's midsection Sunday killed at least 15 people in Texas, Oklahoma, Arkansas, and Kentucky, injuring scores, knocking out power to hundreds of thousands of homes and businesses across the region, and delaying the start of the iconic Indianapolis 500.

Seven deaths were confirmed in North Texas after an apparent tornado tore through Cooke County, near the Oklahoma border, on Saturday night, Gov. Greg Abbott said at a Sunday news conference in Valley View, one of the hardest-hit towns. Two children, aged 2 and 5 years old, were among the dead, according to Cooke County Sheriff Ray Sappington.

At least 100 others were injured in the deadly storm, Abbott said. The governor added that the tornado destroyed more than 200 homes and other buildings as well as damaged another 120 structures.

"I'll be shocked if those numbers are not increased as further assessments are made," Abbott said.

A tornado also ripped through Denton County, northwest of Dallas, on Saturday night and damaged homes and other buildings while knocking down power lines. Officials said "a number of individuals" were injured and transported to area hospitals.

The National Weather Service in Fort Worth said its crews assessed damage and conducted storm surveys in Montague, Cooke, Denton, and Collin Counties.

The tragedy comes five days after tornadoes killed five and injured dozens in Iowa. And at least eight people died when storms slammed Houston less than two weeks ago.

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Developments:

∎ At least five people died in Arkansas, the Associated Press reported. Video and photos posted on social media showed homes destroyed in Decatur, Arkansas.

∎ Severe weather and heavy rain chances shift into the mid-Mississippi, Ohio and Tennessee valleys later Sunday before progressing into the mid-Atlantic, Southeast and Gulf Coast on Memorial Day.

∎ Dangerous and potentially record-breaking heat was forecast to continue across parts of Texas, the western Gulf Coast and southern Florida.

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Dozens sought shelter at truck stop, gas station in Cooke County, Texas

The storm had struck a nearby travel center and gas station complex where more than 60 residents had sought shelter, according to Sappington. Dozens of motorists abandoned their vehicles on a highway and sought shelter at a nearby struck stop as the tornado swept through the area.

Everyone survived but it took rescue teams about an hour to free people who were trapped in the wreckage, according to officials. Search and rescue efforts were also complicated by downed trees and power lines that blocked access to roads, Sappington said.

A National Weather Service official told Reuters that the Valley View tornado packed top winds of 135 miles per hour. Multiple twisters had struck the region, but the exact number had yet to be determined, she said.

Authorities spent Sunday wrapping up initial search-and-rescue operations, according to Abbott. He said authorities were searching for possible additional victims but there were no reports of missing people by the end of the day.

Threat of storms delays Indianapolis 500

Indianapolis Motor Speedway officials delayed the start of Sunday's Indianapolis 500 because of impending inclement weather in central Indiana and asked the 125,000-plus fans inside the venue to exit the grandstands and the Snake Pit and seek shelter. IMS announced approximately 345,000 tickets were purchased for the race.

The race had been delayed at about 11:35 a.m. and rain reached the racetrack at around the time of the originally scheduled 12:45 p.m. start and continued for more than an hour.

"Given the proximity of lightning moving toward (IMS), a decision has been made to pause the pre-race run of show and move fans out of the grandstands and the Snake Pit," speedway officials said in a statement. "Spectators ... should exit the grandstands in an orderly fashion and implement their personal safety plans."

IMS officials cleared fans to return to the grandstands at about 2:05 p.m. Sunday after conditions cleared in the area. Trucks and powerful dryers had circled the track to dry the 2.5-mile oval.

− Nathan Brown and Scott Horner, Indianapolis Star

IMS delays start of Indy 500:Fans asked to vacate grandstands and Snake Pit to seek shelter

Power outages, tornado warnings across Kentucky

In Kentucky, a man was killed Sunday after he was struck by a tree in east Louisville, Louisville Metro Police spokesperson Matthew Sanders said. More than 200,000 homes and businesses across the state were without power Sunday afternoon, hours after a tornado was observed near Mayfield. The town of 10,000 people was hit with a tornado in 2021 that killed at least nine people, The Courier Journal previously reported.

The National Weather Service in Paducah warned that more storms were on the way.

"Several of you are cleaning up after the morning storms and (we) hope that you are safe in doing so!" the weather service said on social media. "Unfortunately, there will be more storms building this afternoon. The storms will be capable of very large hail, 70 mph or greater and tornadoes."

A severe thunderstorm warning for Louisville included "destructive" winds up to 80 mph, according to an alert from the weather service. Earlier, winds of up to 63 mph were reported at the Louisville Muhammad Ali International Airport, the weather service said.

Some storms move on, but dangers remain

Sappington said enough first responders were on the scene in Texas to conduct a thorough search and rescue effort in the storm-ravaged area. He urged people to stay away from the scene.

"I know some people were out of the area and trying to get back, but it's dangerous out there," he said. "Power lines are down. There's been reports of gas leaks. ... We're trying to still rescue people. The best thing people can do right now is give us a little time."  

Fatalities possible in Oklahoma

In the Green Country area of northeastern Oklahoma, kjrh.com reported two deaths in the town of Pryor but had no details. In Claremore, Oklahoma, 30 miles east of Tulsa, police announced the city was effectively shut down because of downed power lines and blocked roads. Dozens of injuries were reported. "Only residents and those with legitimate reasons to enter will be allowed," police said in a social media post. "The cleanup phase is just beginning and will take time."

The National Weather Service office in Tulsa warned the storms were not finished.

"A few strong to severe storms will again be possible this afternoon and evening across portions of far eastern Oklahoma and northwest Arkansas," the National Weather Service office in Tulsa reported. "Large hail and damaging winds will be the primary threats."

Hiding in a cooler in Denton, Texas

In Denton, south of Cooke County, the fire department reported sending a rescue team and medics to a marina on Lake Ray Roberts. "Multiple victims, some reported trapped," the department said on social media, adding that major damage was reported along the county line.

Homes, businesses and boats were battered. Leann Peterson said she thought the storm would roll north of the area. When it didn't, a local business owner suggested people take cover in a restaurant's walk-in cooler.

"We got in the cooler just in time and all these people started coming in, thank God, and when it hit, it was just so loud," she told nbcdfw.com. "It was like something just crashed into us. I didn't realize how bad until we came out."

Contributing: Leo Bertucci, Louisville Courier Journal; Reuters