Super fog contributes to fatal crashes on I-95

As the sun rose Thursday morning, the super fog began to dissipate and a series of crashes could be seen left along Interstate 95 in Volusia County, Florida.

(CNN)Five crashes, two of which killed three people, occurred along a stretch of I-95 in Volusia County, Florida overnight, shutting down an 18-mile stretch of the interstate in both directions.

"Super fog," a combination of dense fog and smoke brought visibility down to less than 10 feet and contributed to the crash, the Melbourne National Weather Service (NWS) tweeted.

"This is a very complex fatal crash scene," Lieutenant Kim Montes, the Florida Highway Patrol spokesperson, said.

According to Montes, the accidents occurred around 1:30 a.m. ET Thursday, with 17 vehicles involved.

Two of the five crashes were fatal, with one death in a crash on the northbound side and two on the southbound side of the interstate.

"That's very unusual to have something like that. We typically only have one side affected," Montes said.

"Miraculously, when you look at some of these cars in the northbound lanes, there are people that survived that (you) don't know how that happened."

The cause of the accident is under investigation, but according to Montes, dense fog and smoke from a prescribed burn in the area brought visibility to zero on the interstate overnight.

"When I came out here two hours after this crash happened, I was doing one mile an hour creeping along the interstate because I could not see in front of my vehicle," Montes said.

Fog could still be seen near one of the crash sites early Thursday morning.

As the sun rose Thursday morning, CNN affiliate WESH had aerials of the crash site and the super fog was still visible near the crash site.

"This is a phenomenon that happens throughout central Florida with our weather when we have the smoke in the fog," Montes added. "Especially when it's cooler, especially the overnight hours."

Super fog forms when a mixture of smoke and moisture released from damp smoldering organic material such as brush, leaves and trees, mixes with cooler, nearly saturated air.

Smoke from the prescribed burn happening in the area yesterday would be necessary for creating super fog.

"The area was under what is called a temperature inversion," explained CNN meteorologist Chad Myers. "Normally, air gets colder as you go up in altitude, but in this case, the temperature actually rose significantly just above the surface. This created a trap, of sorts, that did not allow the smoke to rise up from the ground making the fog even denser. "

A recent study worked toward a better understanding of how super fog forms so forecasters may be able to a may be able to add additional criteria in planning future prescribed burns.

While it is now known how super fog forms, co-author of the study Marko Princevac cautioned, "It is still early to claim that super fog can be predicted with any certainty."

Super fog has caused several large pileups in Florida, including on I-4 near Davenport in 2008 and one on I-75 south of Gainesville in 2012, the NWS in Melbourne said.