FORT LAUDERDALE, Fla. >> The church van headed south — packed with children, an hour to go before reaching Walt Disney World after a 700-mile trip from Louisiana. A semi-truck rumbled nearby.

In Interstate 75’s northbound lanes Thursday afternoon near Gainesville, another semi and a car smashed into each other, the Florida Highway Patrol says. The velocity and weight of that now out-of-control semi burst through the metal guardrail, taking the car with it.

The two semis, the van, and the car slammed into each other, diesel fuel leaked and the mass erupted in a fireball. A fifth car, unable to avoid the chaos, sped through, possibly hitting victims ejected from the vehicles, the highway patrol said. Five of the children, ranging from about 8 to teenagers – from a church in Marksville, Louisiana – and the two truck drivers died. At least eight others were injured, some seriously.

“It is a heartbreaking event,” Lt. Patrick Riordan said today.

Identities of the victims have not been released. Riordan said the cause of the initial crash remains under investigation.

The accident occurred on a clear day along a straight, flat stretch of Interstate 75 outside Gainesville, the home of the University of Florida. It is a busy stretch of a highway that connects Florida to the rest of the South, Indiana, Ohio, and Michigan.

Its lanes fill daily with semis carrying produce and goods that barrel among cars, vans, and buses filled with tourists headed to and from Orlando, Tampa, and southern Florida.

Vinnie DeVita said he was driving south and narrowly escaped the crash — he saw it in the rearview mirror, immediately behind him, according to a report by WKMG .

“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.”

Nicole Towarek was traveling northbound with her family when they came across the scene. She told the Gainesville 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.

“We kept seeing these little explosions and fire,” she said. “The heat, it was insane.”

The National Transportation Safety Board would normally send a team to help with the investigation, but cannot because of the federal government shutdown. Riordan said today that will not impede the highway patrol’s efforts, which could take months.

Florida Department of Transportation Troy Roberts said the agency is investigating whether the guardrail should have stopped the northbound crash from crossing the highway or whether the crash was too traumatic.

“The guardrails are there to stop as much as they can, but there are some things they cannot,” Roberts said. “Unfortunately, in this case, they did not.”

It was the worst accident on I-75 in Alachua County since January 2012, when 11 people died in a chain reaction crash attributed to heavy fog and smoke on the roadway, which crosses Paynes Prairie Preserve State Park.

Officials were criticized then for not closing the road due to worsening conditions, and later installed cameras, sensors and large electronic signs to help prevent similar crashes.