Clark County Coroner Michael Murphy says IndyCar driver Dan Wheldon died of blunt head trauma after a spectacular 15-car wreck at the Las Vegas Motor Speedway.

Murphy tells The Associated Press that an autopsy Monday found the 33-year-old two-time Indianapolis 500 winner died of head injuries at the Las Vegas hospital where he was taken after Sunday's crash. Murphy ruled it an accident.

Wheldon was pronounced dead at 1:54 p.m. Sunday at University Medical Center in Las Vegas.

The race was called off after Wheldon's death.

Other drivers released from hopsital

Two IndyCar drivers have been released from a Las Vegas hospital after overnight treatment for injuries they received in the same crash that killed Wheldon.

IndyCar officials say Pippa Mann and JR Hildebrand were released Monday from University Medical Center.

IndyCar spokeswoman Tracey Todd says the 28-year-old Mann underwent surgery for a burn to her right pinkie finger received in the 15-car wreck Sunday at Las Vegas Motor Speedway. Mann is from London.

Officials say Hildebrand was held overnight for evaluation. The 23-year-old American driver was treated for a bruised sternum.

Will Power, a 30-year-old Australian, was evaluated at the hospital Sunday and released.

The Clark County coroner was conducting an autopsy Monday for Wheldon.

The 33-year-old Englishman died of his injuries after the crash.