DAYTONA, Fla. -- The Daytona 500 was red-flagged Sunday after 38 laps because of a brief rain shower.

But shortly after the track began to dry, it started raining hard and was still raining hard at 3 p.m. ET.

A tornado warning was issued for the area, including Daytona International Speedway, until 3:45 p.m. The grandstands were emptied with thunder and lightning in the area.

Kyle Busch was leading at the time of the red flag followed by Kasey Kahne, Denny Hamlin, Brian Vickers, Paul Menard, Brad Keselowski, Jeff Gordon, Joey Logano, Ricky Stenhouse, Jr., and pole-sitter Austin Dillon.

Dillon led the first lap before Hamlin took over command of the race. But Hamlin's car started overheating after a piece of paper flew onto his grill. With water temperatures reaching 290 degrees, Hamlin was forced to drop out of the lead in an attempt to get behind another car and use the draft from the other car to remove the paper. It worked.

The first yellow flag came out on lap 22 when rookie Kyle Larson spun in turn two. Larson had hit the wall on lap three.

Things got really crazy a lap later when all of the cars headed for pit road.

First, Matt Kenseth could not see his pit sign at first. When he did, he had to jam on his brakes as he spun backwards into his pits. His crew was forced to work on the car as it headed in the wrong direction.

A moment later, Marcos Ambrose and Danica Patrick touched as Ambrose left his pit stall after a quick stop for gas and Patrick tried to get into her pits.

Another yellow flag flew on lap 30 when Martin Truex, Jr. suffered a blown engine.

"I went to bed thinking this was the best shot I've ever had at winning the Daytona 500," Truex said. "We had such a great car. That is why this is such a shame. Something knocked the fuel pump off."

Truex will finish 43rd.