Leader Allgaier, Hamlin part of 20-car crash at Daytona 500 - ESPN

DAYTONA BEACH, Fla. — The «Big One» happened earlier than usual at the Daytona 500 on Sunday: a 20-car crash just past the midway point that involved three-time race winner Denny Hamlin and several other contenders.

Justin Allgaier was leading in a car once fielded by two-time race winner Dale Earnhardt Jr. when Hamlin tried to pass on the outside at Daytona International Speedway. Allgaier threw a late block and squeezed Hamlin into the wall, igniting the melee with seven laps remaining in the second stage of NASCAR's season opener.

Hamlin, trying to become the third driver to win four Daytona 500s, spun into the infield grass. Former race winner Michael McDowell, Alex Bowman, Shanevan Gisbergen, Ross Chastain, Erik Jones and John Hunter Nemechek were among those involved.

Two-time Daytona 500 runner-up Bubba Wallace slipped through the wreckage unscathed, took the lead and won the stage under caution. Wallace drives for 23IX Racing, which is owned by Hamlin and Pro Basketball Hall of Famer Michael Jordan.

The start of the race was moved up an hour in hopes of avoiding afternoon showers that are expected in the area.

Kyle Busch, driving the No. 8 Chevrolet for Richard Childress Racing, led the field to the green flag in hopes of winning «The Great American Race» for the first time in 21 tries. He holds the race's longest active skid.

William Byron is trying to become the first driver in history to win the Daytona 500 three consecutive years. But Byron had to switch to a backup car following a qualifying crash and landed on pit road in the opening laps Sunday after B.J. McLeod spun in front of him, leading Byron to hit the outside wall.

Byron won last year's event in overtime after race leader Hamlin got spun on the