INDIANAPOLIS (AP) — Ryan Briscoe is out of the Indy 500 after a wreck in turn four.

The Penske driver had just re-entered the track following a pit stop when he failed to negotiate the final turn on the 2.5-mile oval.

The 28-year-old Australian qualified fourth and entered the pits with the lead. He was still getting back up to speed when the crash occurred. Team owner Roger Penske says he's not sure what happened.

Briscoe was making his fifth start in the 500 and had run a flawless race behind leader Dario Franchitti. His No. 6 car was getting better gas mileage than the rest of the leaders.

Penske's two other drivers, three-time champion Helio Castroneves and Will Power, both struggled with pit problems earlier in the race.