For three hours early Sunday morning, the Florida Highway Patrol shut down a stretch of Interstate 75 outside Gainesville because fog and smoke from a nearby prairie fire had made it too dangerous to drive.
Then at 3:26 a.m., officials reopened the interstate.
One of the deadliest crashes in Florida history started about 30 minutes later.
The smoke and fog quickly rolled back in, officials said, causing nearly two dozen vehicles to collide. Ten people were killed and more than 20 were hospitalized after a series of fiery wrecks that littered northbound and southbound I-75.
"Sometime after the roadway was reopened," Lt. Patrick Riordan said, "the conditions changed very quickly."
As troopers continued to identify the dead and inform their families Monday, the FHP said it will investigate the decision to reopen the interstate instead of leaving it closed until daylight.
But Riordan, speaking Monday at a news conference broadcast from Marion County, also said that those troopers appeared to have done the job they were trained to do. They used their training and experience to close and reopen the road, never left the area and kept monitoring road conditions and visibility.
"We believe our troopers did their due diligence to keep our highways safe," he said.
Gov. Rick Scott also announced Monday that he asked the Florida Department of Law Enforcement to investigate Sunday's events.
"We will also fully cooperate with any federal investigation which may occur," Scott said in a prepared statement. "During this tragic time, our thoughts and prayers should be with the victims and their families."
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Nearly two dozen vehicles were involved in the crash, including at least six semitrailer trucks. The FHP investigation is treating the northbound and southbound crashes separately. But on Monday, officials started releasing reports that described some of the crashes and identified some of the victims:
A 2006 Freightliner semi driven by Monroe Millwood, 58, of Georgia was headed south on I-75 when he stopped in the right outside lane as visibility plunged to zero and crashes were already littering the roadway. A 2011 Volvo semi driven by Cynthia Laird, 44, stopped in the center lane.
Then a vehicle with two occupants (troopers didn't say what kind of vehicle it was) slammed into the rear of the semi in the right outside lane. A 2004 Ford SUV driven by Shelise Bellow, 27, crashed into the back of the first vehicle, according to the FHP report.
A 2008 Dodge truck driven by Richard Szabados, 39, of Silver Springs then struck the rear of the Volvo semi in the center lane. A second vehicle, driven by an unknown person, then crashed into the back of the Dodge.
A fire erupted amid the wreckage and consumed all the vehicles except for the Freightliner and the Volvo cabs. They were unhooked from their trailers after the crash and were able to drive off the roadway.
The occupants of the Ford SUV and the Dodge truck also escaped. But three people died. They have not yet been identified.
"They were burned very, very severely," Riordan said, "to a point where positive ID has been a hurdle for us."
According to the Gainesville Sun, some of Sunday's victims included six members of a family from Georgia. Five of the family members died and another was in critical condition. The family was returning home from a church conference in Orlando.
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FHP Sgt. Steve Gaskins, who patrols the Tampa Bay area, said a lot goes into the decision to close or open a road based on visibility.
"It's never a snap decision," he said.
He said troopers will drive through the areas, monitoring the conditions and closely watching the weather forecasts. They also rely on the Low Visibility Occurrence Risk Index (LVORI.) It's a system developed in Florida that determines the probability of low visibility based on weather conditions and smoke density. But those calculations can change quickly, Gaskins said.
"In low-lying areas, fog can roll in very, very quickly, and within a few seconds weather conditions can change," he said.
When visibility drops suddenly, Gaskins said, drivers should dim their headlights and slow down, but not stop. The problem on major highways like I-75 is when fog and smoke set in, people are traveling too fast to react properly.
"If you're traveling 70 miles per hour, for example, that's 102 feet per second," Gaskins said. "If you can't see 5 feet in front of your car, you shouldn't be going that fast."
But when smoke or fog has reduced visibility to zero, the state recommends that drivers signal that they're turning off the road, drive as far off the pavement as possible and activate their hazard lights.