The incident closed the Turnpike for about four hours and backed up traffic for miles as law-enforcement and hazmat crews investigated.
A Florida Highway Patrol trooper noticed a white SUV that had hit a guardrail near Mile Marker 224 about 3:15 p.m., the Osceola County Sheriff’s Office said.
The trooper went inside the vehicle and found two people dead, Sheriff’s Office spokeswoman Twis Lizasuain said.
The damage to the vehicle was minor and investigators do not think the deaths were caused by the crash, Lizasuain said.
The Sheriff’s Office was called to investigate. Two deputies also became exposed to the substance inside the vehicle.
All three were treated and taken to the hospital as a precaution. They are expected to be OK.
The two people who were found dead have not been identified.
The medical examiner’s office will be investigating the cause of death and helping to identify the unknown substance.
Lizasuain said the substance didn’t appear to be drug-related. She said they will be doing a forensic scan of the vehicle to help piece together what happened.
“At this time, the investigation does not appear to be criminal in nature, but the autopsies are going to be instrumental as we continue to investigate,” she said.
The closure had traffic backed up for miles.
Daniel Harris, 41, was traveling from Georgia to Fort Lauderdale to deliver a camper when he was stopped just a few vehicles behind the incident.
He said he’d been sitting in traffic since about 3:30 p.m. and watched the large law-enforcement response.
Harris said authorities went inside the vehicle, trying to help the two people inside.
“One officer came out of the car with a bunch of stuff all over him,” Harris said.
About 15 police vehicles, five highway patrol vehicles and several fire trucks responded to the incident, he said.
“It looks like a pretty minor accident,” he said. “The vehicle is barely touching the rail. I don’t know what happened to cause two people to die, but it definitely wasn’t the crash.”