It's a combination of dense fog and smoke and it was present in southeast Louisiana Monday morning and contributed to near-zero visibility in some places.
Troopers are investigating a 21-vehicle chain-reaction crash that killed three people on Interstate 75 in North Florida, which happened just after midnight on New Year's Day. While FHP has not yet said what started the massive collision, the National Weather Service had issued a dense fog advisory for the area just three hours before the crash, warning drivers that firework smoke could mix with the fog, resulting in "near-zero visibility."