Jaylene Vargas-Gonzalez was found in the back of her delivery truck on Aug. 10 after a Fruitland Park resident noticed the vehicle had been parked near the end of his driveway for several hours with its engine still running. The Lake County Sheriff's Office released the cause of death on Friday.

According to the autopsy report, Vargas-Gonzalez's blood carboxyhemoglobin saturation — a measure of carbon monoxide in the bloodstream — was 58% at the time of her death. Testing of the van's interior with the engine running also revealed elevated carbon monoxide levels inside the compartment. The autopsy found no evidence of traumatic injury and no signs of natural disease.

Patrick Miranda, the resident who called authorities, said he grew suspicious when he saw the truck idling but apparently empty.

"I see the phone is still plugged in. The backpack is there and again the car is running, but there is no one," Miranda said. "It seemed kind of strange."

Surveillance video from Miranda's home captured deputies and Lake County Fire Rescue arriving at the scene. Miranda said a deputy opened the passenger-side door first and recoiled from fumes before opening the rear sliding doors and finding Vargas-Gonzalez unconscious inside.

"The police officer opened the passenger side front and he had some fumes, he had to reel back from," Miranda said. "Then he opened the back, the sliding doors, and she was lying there in the back unconscious."

Miranda said one of the deputies also appeared lightheaded after approaching the truck. Fearing potentially toxic substances, firefighters in gas masks responded and secured the area. Vargas-Gonzalez was rinsed with a fire hose before paramedics began life-saving measures, Miranda said.

"Because they were worried about toxic chemicals, I remember they did use a fire hose to rinse her off to make sure there was nothing on her clothes or person," he said. "But immediately after that, they were using life-saving measures."

Vargas-Gonzalez was taken to a hospital, where she died.

Amazon said in a statement after her death that the company was "deeply saddened by this tragic incident" and that its "thoughts and prayers are with the driver's loved ones during this difficult time." The company said it was cooperating fully with local authorities in their investigation.

The case highlights a hazard that safety advocates say is often overlooked in the grueling, vehicle-centered work of package delivery: carbon monoxide can build up inside a running van, particularly when a driver rests or works in the cargo area. The gas is colorless and odorless, and prolonged exposure can cause confusion, loss of consciousness and death.

Vargas-Gonzalez's death remains under review by the sheriff's office, which has classified it as an accident.