At least seven people were killed and seven others were injured Thursday in a multivehicle crash on Interstate 75 near Gainesville, Florida, investigators said.

The Florida Highway Patrol said two tractor-trailer rigs and two passenger vehicles were involved in the crash, which unfolded about a mile south of Alachua. Alachua County Fire Rescue reported that flames ignited after 50 gallons of diesel fuel spilled on the highway.

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

CLICK HERE TO GET THE FOX NEWS APP

Fire Rescue said in a Facebook post that "multiple patients" had suffered "critical injuries," but did not specify how many. Authorities initially said six had died but late Thursday night revealed a seventh victim had perished.

At one point, the Alachua County Sheriff's Office dispatched a helicopter to look for potential victims in the woods off the highway.

"Two semis were involved and on both of them at least the trailer part has burned," Florida Highway Patrol Lt. Patrick Riordan told The Gainesville Sun. "At least some of the fatalities were in at least one of the passenger vehicles."

Riordan told The Associated Press it was unclear whether the victims were killed in the wreck or whether they burned in the fire, which would make identification more difficult.

SLAIN OFFICER'S WIDOW OUTRAGED AFTER KILLER GRANTED APPEAL

I-75 was closed in both directions due to the severity of the crash, causing massive delays. Debris including personal property and vehicle parts was scattered across the road, the Florida Highway Patrol said.

The crash was in the northbound lanes, but southbound lanes were closed for hours to keep a route open for first responders, according to a tweet from the Alachua County Sherriff's office, which said the emergency "required all hands on deck." Authorities opened the northbound lanes around 8 p.m.

"There are engine parts and components, and there is a lot of area that is burned,” Riordan told The Sun. “Contamination of fuel is a high probability at this point."

The Associated Press contributed to this report.