DAYTONA BEACH, Fla. (AP) - Dale Earnhardt Jr. started a 12-car accident at Daytona International Speedway that essentially shut down a three-day test session.

NASCAR's most popular driver tapped Marcus Ambrose as they drove across the back straightaway, lifting him ``like a forklift'' and turning him into the wall. Ambrose's car bounced back across the track and collected a host of others.

Two of Earnhardt's Hendrick Motorsports teammates, Jeff Gordon and Kasey Kahne, also were involved. So were defending Sprint Cup champion Brad Keselowski, new teammate Joey Logano, Carl Edwards, Kyle Busch, Jamie McMurray, Martin Truex Jr., Aric Almirola and Regan Smith.

Kahne's car sustained significant damage.

The wreck caused several teams to pack up and leave Daytona, and ended the pack racing that NASCAR wanted to see to evaluate its redesigned cars.