The so-called “super fog,” which US media reported was caused by a mixture of marsh fires and dense fog, led to a massive pileup on Interstate 55, about 30 miles (48 kilometres) outside of New Orleans, the Louisiana State Police said in a statement.
Photos posted by the police showed both lanes of the highway bridge where the incident occurred blocked off by the wreckage, which included dozens of charred vehicles. A fire had erupted on the highway, police said.
One vehicle appeared to have driven off the bridge and into the water below.
More than 25 people were taken to hospital, not counting the “many victims (who) sought medical assistance on their own.” Super fogs form “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,” according to the National Weather Service.
When they occur, visibility can drop to less than 10 feet (three metres).Louisiana state police shared aerial photos on their Facebook page showing the crashed cars and extensive debris on both northbound and southbound lanes of the elevated interstate, which passes over swamp and open water between Lake Pontchartrain and Lake Maurepas.
As of Monday afternoon, state troopers were still working “to notify families, investigate the exact causes of the crashes” and coordinate with the state’s transportation department to have the bridge inspected, Louisiana state police said in a social media post.
Traffic backed up for miles in both directions on I-55. The lack of visibility also prompted closures of parts of Interstate 10 and the 24-mile (39km) Lake Pontchartrain Causeway at times.
School buses were summoned to transport stranded motorists from the accident sites. At midday, state police told reporters at the scene that one vehicle went over the highway guardrail and into the water, but the driver escaped unharmed.
The National Weather Service warned that a dense fog advisory would be in effect into Tuesday morning for parishes near lakes Pontchartrain and Maurepas.
