Two skydivers were killed during a jump in Northern California Saturday morning, according to authorities.
The bodies were found in a vineyard in Acampo, about 30 miles south of Sacramento, San Joaquin County Sheriff's Office Lt. Randy Johnson said.
Johnson said the sheriff's office got the call about the incident at about 10 a.m. (1 p.m. ET). Witnesses told NBC affiliate KCRA in Sacramento that they did not see a parachute open.
Johnson said the relationship between the victims, who have not been identified, was unclear, but amateur skydivers are often required to jump with an instructor.
The skydivers were jumping with the Parachute Center skydiving school in Acampo, where an introductory tandem jump with an instructor from 13,000 feet costs $100. Parachute Center owner Bill Dause told KCRA the instructor was an independent contractor, but he was very experienced.
"The parachute failed to eject properly. We have no explanation why," Dause said "The only thing it looks like is something may have gone out of sequence. That may have caused the problem."
The Federal Aviation Administration is investigating the cause of the incident, Johnson said.