Carlos Gonzalez, spokesman for the Chihuahua state prosecutors’ office, said the driver appeared to have lost control of the truck – with tyres said to be nearly 5ft high – after leaping over a pile of cars it was crushing during a demonstration at the Extreme Aeroshow.
The incident late on Saturday afternoon took place at the El Rejon dam on the outskirts of Chihuahua, about 230 miles south of Mexico’s border with the United States.
Some local media reported the death toll had risen to 13, but there was no official confirmation.
The dead included two girls aged 6 and 7 and a 12-year-old boy, according to the city government’s official Facebook page.
A preliminary investigation suggested the accident was because of to a “technical error,” an official said, adding the driver has been detained.
Some witnesses said the driver appeared to have hit his head on the interior of the truck as he drove over the old cars.
Eyewitnesses described seeing the driver’s helmet come off before the massive vehicle drove into the crowd of terrified spectators, who tried to flee.
“I fell over and when I turned around I saw the tyre very close. It hit me and threw me to the other side,” Jesus Manuel Ibarra, 41, said as he was treated for injuries to his arm and hip.
Mr Gonzalez said the accident killed at least one child and hurt 80 people, 46 of whom remained hospitalised early yesterday morning.
He said the number of dead and injured could rise as officials received updated information.
The local health system listed the names of 67 injured people on its Facebook page, calling urgently for blood donations and help from local doctors and nurses.
Mr Gonzalez said prosecutors were looking into the possibility of a mechanical failure that left the driver unable to release the accelerator.
Several witnesses, however, confirmed that the driver appeared to have become incapacitated when he struck his head during the show, in which the truck drives at high speed at smaller cars, crushing their roofs as it lands on them.
Spectator Daniel Dominguez, 18, said he was happily watching the show with a group of relatives when the truck came down hard in the middle of the cars.
“The driver hit his head and his helmet flew off,” Mr Dominguez said. “The truck came directly at where we were.”
His 11-year-old sister was in surgery for injuries to her legs and his mother was treated for minor contusions.
The air show was cancelled following the accident, which happened during the second day of the three-day event.