The singer was hit by a cartridge from a pyrotechnic device. She was taken to a hospital where she was later pronounced dead, the outlet reported, citing Spanish newspaper El Diario Montañés.
Sainz Garcia, 30, was performing with the Super Hollywood Orchestra on the final night of a four-day festival held in Las Berlanas, near Madrid. She was part of a 15-person group that was performing for around 1,000 fans when the explosion occurred.
The paper reported that a doctor and nurse who were in the audience attended to the singer while waiting for paramedics.
Prones 1SL, the group’s promoter, said the incident was likely the result of a manufacturing error with the explosive, according to newspaper El Norte de Castilla. The company’s owner Isidro López told El Diario Montañés that he had been using the pyrotechnics “for five or six years” without incident.
In a Facebook post, the company wrote: “From the direction of the company Prones 1SL agency that represents the Super Hollywood Orchestra and all our staff, musicians, assembly and artists in general, [we] express our most heartfelt condolences to the family and friends for the loss of our colleague Joana.
“We will always remember you, Joana. R.I.P.”