The wreck happened on I-75 about a mile south of Alachua, near Gainesville. The Florida Highway Patrol said Friday that the children were 14-year-olds Joel Cloud and Jeremiah Warren, 13-year-old Cara Descant, 10-year-old Briena Descant, and 9-year-old Cierra Bordelan. All were from Marksville, Louisiana, and were in a Pentecostal church van headed to the theme park when the accident happened Thursday afternoon outside Gainesville.
"It's unbelievable. Everybody is in shock. We lost five of our children," church member Maxine Doughty told the Associated Press. "We had our Last Supper Sunday, and the pastor said to live our lives like each day is the last day."
An official for the church said pastor Eric Descant's 50-year-old wife, Karen, was critically injured, and his granddaughter was among the dead.
The truck drivers were 49-year-old Douglas Bolkema of Albuquerque, New Mexico, and 59-year-old Steve Holland of West Palm Beach.
The highway patrol says Holland's truck was traveling north in the far-right lane and truck suddenly veered left, colliding with a car driven by Robyn Rattray, 41, of Gainesville.
Both the truck and car went out of control and through the center divider, where Holland's truck plowed into the southbound church van, driven by Amy Joffiron, 49, causing it to flip several times and eject some of the nine children on board. The highway patrol said it is unknown if any were wearing seatbelts.
The van and Bolkema's truck collided with the semi and the car and burst into flames. Diesel fuel leaked, and the mass erupted into a fireball, the Florida Highway Patrol said.
The cause of the crash, which happened on a clear day on a straight, flat stretch of Interstate 75, remains under investigation.
The children were traveling in a passenger van from Louisiana, according to Lt. Patrick Riordan of the Florida Highway Patrol. When asked where they were headed, he said, "My information is that they were destined for Disney."
The accident happened when the van was about an hour north of the theme park.
The children's church, United Pentecostal Church in Marksville, Louisiana, confirmed that the children were headed to Disney World. In a statement on Facebook, the church's district office asked for prayers.
Injured victims, including children and adults, were taken to two different hospitals, according to FHP. The number of injuries is still being confirmed.
Rattray and Joffiron suffered serious injuries, as did the four surviving children, who were also ages 9 to 14. They remain hospitalized, as did Karen Descant.
Emergency crews extinguished the fire and said they were treating the crash as a homicide investigation, but didn't say why.
Court records show Holland received numerous tickets between 2000 and 2014 in Florida, Pennsylvania, Ohio, Indiana and Virginia for violations such as speeding, driving an unsafe vehicle, driving an overloaded vehicle and not carrying proof of insurance. Bolkema received a ticket in 1997 for following too closely.
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 Orlando television station 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."
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.
"There's going to be families that need to be notified that their loved ones have perished," said Lieutenant Patrick Riordan.
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 National Transportation Safety Board would normally send a team to help with the investigation, but cannot because of the federal government shutdown. Riordan said that will not impede the highway patrol's efforts, which could take months.
Florida Department of Transportation spokesman 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 severe.
"The guardrails are there to stop as much as they can, but there are some things they cannot," Roberts said.
The aftermath closed part of the highway in both directions, causing massive delays.
Debris including personal property and vehicle parts was scattered across the road, the Florida Highway Patrol said.
The Associated Press contributed to this report.