'Super fog' in Louisiana leads to deadly crashes along I-55 near New Orleans

At least two people are dead and 30 are injured after "super fog" caused pileups on a stretch of Interstate 55 in Louisiana.

The fatalities and injuries resulted from about 25 different vehicle crashes Monday along I-55 west of New Orleans between Ruddock and Manchac, St. John the Baptist Parish Sheriff Mike Tregre told CNN affiliate WVUE. The stretch of highway runs between Lake Maurepas and Lake Pontchartrain.

Tregre said two fatalities were confirmed as of Monday afternoon.

In the northbound lanes, about three 18-wheel trucks collided and were fully engulfed in flames, Tregre told WVUE. In the southbound lanes, there were two reported multi-car pileups, one of which was also producing flames.

Tregre said one vehicle was pushed over the railing of the interstate, but those inside "appear to be fine."

According to Tregre, all first responders are on foot because the crashes have left the area "completely gridlocked." He said rescue efforts "will take a while."

"The situation is pretty bad," he added.

Visibility levels were below a quarter mile at a nearby weather station from just after 4 a.m. CDT until just before 10 a.m. CDT. Visibility likely neared zero at times throughout the morning when the fog was at its densest.

The incredibly dense fog, known as "super fog," was caused by fog combining with smoke from nearby fires. Super fog is a thick fog that develops in damp, smoky conditions and can send visibilities plummeting to less than 10 feet, according to the National Weather Service.

Louisiana has battled unprecedented wildfires, extreme heat and relentless drought since the summer. Exceptional drought, the highest category tracked by the US Drought Monitor, is in place across 62% of the state.

In a statement Monday, the city of New Orleans said it is monitoring an active fire burning underground in forested wetlands between Bayou Sauvage National Urban Wildlife Refuge and the Michoud Canal.

The lack of rain combined with the summer's extreme heat dried out wetlands and reduced the water table's depth, the city said. The blaze being monitored has been burning at and below surface level, it added.

A repeat of Monday's super fog is unlikely for Tuesday morning as "winds should be much stronger," the National Weather Service in New Orleans said Monday on X, previously known as Twitter. Winds need to be calm or very light in order for dense fog to form.

Patchy areas of dense fog may be possible but will not be as widespread as Monday, the city said, citing the weather service.