RENO, Nev. — The death toll rose to nine Saturday in an air race crash in Reno as investigators determined that several spectators were killed on impact as the 1940s-model plane appeared to lose a piece of its tail before slamming like a missile into a crowded tarmac.

Moments earlier, thousands had arched their necks skyward and watched the planes speed by just a few hundred feet off the ground before some noticed a strange gurgling engine noise from above. Seconds later, the P-51 Mustang pitched oddly upward, twirled and took an immediate nosedive into a section of white VIP box seats.

The plane, flown by a 74-year-old veteran racer and Hollywood stunt pilot, disintegrated in a ball of dust, debris and bodies as screams of “Oh my God!” spread through the crowd.

National Transportation Safety Board officials were on the scene Saturday to determine what caused Jimmy Leeward to lose control of the plane, and they were looking at amateur video clips that appeared to show a small piece of the aircraft falling to the ground before the crash. Witnesses who looked at photos of the part said it appeared to be a “trim tab,” which helps pilots keep control of the aircraft.

“Pictures and video appear to show a piece of the plane was coming off,” NTSB spokesman Mark Rosekind said at a news conference. “A component has been recovered. We have not identified the component or if it even came from the airplane ... We are going to focus on that.”

The dead so far included the pilot and eight spectators. More than 54 people were seen at hospitals. Eight remained in critical condition and nine were in serious condition.