Two big rigs and two passenger vehicles collided and spilled diesel fuel across a Florida highway Thursday, sparking a massive fire that killed seven people and injured at least eight others, authorities said.

Emergency crews extinguished the fire and authorities said they were treating the crash as a homicide investigation, but didn’t say why. The fire was so intense that authorities said it damaged parts of the road.

A spokesman for the Florida Highway Patrol told The Associated Press in a phone interview that their top priorities were to conduct a thorough investigation and to identify the deceased victims.

The wreck happened on southbound Interstate 75 about a mile south of Alachua, near Gainesville. The flames were fed by about 50 gallons of diesel, authorities said.

Authorities initially said six had died but late Thursday night revealed a seventh victim had perished. At least eight others were hospitalized, some with critical injuries, the Gainesville Sun reported. FHP Lt. Patrick Riordan said early Thursday evening that five of the accident victims who died were in a passenger van, and another person who died was in one of the tractor-trailers.

“If I had stepped on the brake when I heard the noise, undoubtedly, I would have been in that accident,” DeVita said. “And then within probably 15 to 20 seconds of it all, it exploded. I mean, just a ball of flames.”

It’s unclear whether the victims were killed in the wreck or whether they burned in the fire, which would make identification more difficult, he said.

The aftermath closed part of the highway in both directions, causing massive delays. Authorities opened the northbound lanes around 8 p.m. but southbound lanes remained closed Friday morning. Debris including personal property and vehicle parts was scattered across the road, the Florida Highway Patrol said. A helicopter helped search for any victims who may have been in nearby woods.

Nicole Towarek was traveling northbound with her family when they came across the scene. She told the Sun that black smoke billowed, people were laid out near vehicles, there were long skid marks across the roadway and emergency workers were converging on the area.