They say the wreck occurred around 8:10 a.m. in the westbound lanes of the interstate. They say seven commercial vehicles were involved, including an empty tanker truck that ruptured and caught fire.
State troopers say it's one of the worst crashes they've ever seen.
"Having walked through the scene, I'm surprised we didn't have more deaths," said one trooper.
One driver told FOX 5 that the smoke was thick. The motorist says they ran up on it and pulled over to the side when someone hit them.
Troopers say Michael Jarome Smith, 52, of Covington, Joel Moore of Effingham County as well as Clayton and Josephine Warnock, both of Dublin, died from injuries sustained in the crash. Nine people were injured.
Smith's son said that his father was the safest driver he knew. He says the 52-year-old FedEx driver was hard-working with lots of goals and aspiration and he says he truly loved his family.
Reginald Smith lived next door to the driver.
"We had these 12 or so years in the neighborhood together. He was a neighbor I could trust. I am really going to miss Michael," said Reginald Smith.
Michael Smith is survived by his parents and three adult children.
FOX 5 has learned a DOT crew had already been asked to put up warning signs about the foggy conditions on Wednesday morning, but the deadly crashes happened before those workers and signs reached the scene.
The Georgia State Patrol says their investigation could take months.
"When you think of four fatalities, when you think of the number of vehicles involved and all of what needs to be documented, you can turn around and six months will go by," said Col. Mark McDonough of the Department of Public Safety.
One westbound lane remains closed to traffic. It is not known when it will be reopened.