POLK COUNTY, Fla. -- A 35-year-old worker at Disney's Animal Kingdom park was identified as one of four people killed in a 70-car pileup in Polk County as officials continue to search for an official cause.

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A chain-reaction series of crashes on a stretch of Interstate 4 between U.S. 27 and Polk Parkway happened at about 4:30 a.m. in foggy conditions and after a nearby prescribed burn apparently grew out of control during unexpected weather.

Scott Snyder, who was a newlywed, was traveling from Lakeland to Disney to get to his 6 a.m. shift when he was killed.

"He was a delight to us and there is going to be a big hole in our lives," the victim's mother-in-law Mary Ussery said. "He was the kind of person who made your face light up."

Ussery said she broke the news of Snyder's death to her daughter.

"It was one of the worst things I've ever had to say to her," Ussery said. "I feel he is in Heaven right now with God and looking down and probably trying to comfort his wife and wipe some of her tears away."

The identities of the three other people killed in the crash have not been released. Officials said 38 people were also injured in the pileup.

No Official Cause

Meanwhile, investigators are poring over evidence trying to determine what caused the fatal crashes and why drivers were apparently caught off guard.

State officials said a prescribed burn clearly affected the roadway early Wednesday but denied it was let out of control, Local 6's Chris Trenkman reported.

The Florida Division of Forestry said it foresaw a smoke problem going into the night and ordered warning signs installed along I-4.

"There was a change in weather conditions that was unexpected from the weather reports that we received earlier," Florida Division of Forestry representative Gary Zipperer said. "Humidity dropped extremely low, which created problems with (fire) control."

Zipperer said as soon as Game and Fish officials realized they had control problems they called the Florida Division of Forestry for help.

"We have our investigative team out there and we are looking at all kinds of things, (including) weather for that night, fuels on the ground," Zipperer said. "We are going to do an in-depth investigation into this and we are not at liberty to say that smoke caused this accident."

Polk County Sheriff Grady Judd said he was "exceptionally concerned" about the decision to start a fire during dry conditions and days after a freeze likely added more tinder.

I-4 Work Needed

The stretch of I-4 remained closed to traffic in both directions in Polk County.

Work crews said they must repave parts of the road because of the extreme damage.

Officials said the road could be opened by rush hour Thursday but be prepared for delays in the area.

Deputy: 'I Watched Man Burn'

One of the first sheriff's deputies at the pileup said he could not reach people trapped and burning in their vehicles.

""(The officer) said, 'I did all I could do but I watched a man burn to death today and I heard others screaming and crying,'" Polk County Grady Judd said. "And (the officer) said, 'I can't begin to explain to you how difficult this scene was and I can't begin to explain to you the trauma that occurred, and I did all I could.'"

Judd said visibility was zero before the series of crashes.

"We have a major disaster that has occurred on Interstate 4," Judd said. "Our firefighters and EMTs went into an environment where you could not see absolutely anything in front of you. It was as if you were hitting a wall of smoke and fog. As a result of that, there have been at least 50 vehicles involved in the major event. You could not see your hand in front of your face and that is not an exaggeration."

More than 100 emergency units were called to the crash scene to assist the injured.

Watch Local 6 News for more on this story.