NEW ORLEANS (AP) — A “superfog” of smoke from south Louisiana marsh fires and dense morning fog caused multiple traffic crashes involving scores of cars Monday, turning Interstate 55 near New Orleans into a narrow junkyard of mangled cars and trucks, some of them burning.

State police said they could not confirm whether there were any fatalities and they had no information on the number of injured. The Blood Center of New Orleans posted a call for blood donors in the wake of the multiple accidents.

Traffic backed up for miles in both directions on I-55 near the community of Manchac. The lack of visibility also prompted closures of parts of I-10 and the 24-mile (39-kilometer) Lake Pontchartrain Causeway at times.

School buses were summoned to transport stranded motorists from the accident sites on the elevated I-55, which passes over swamp and open waters between lakes Pontchartrain and Maurepas. 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.

Clarencia Patterson Reed said she was driving to Manchac with her wife and niece in the car when she saw people waving their hands for her to stop. She said she stopped the car but was hit from behind and on the side by two other vehicles.

“It was ‘Boom. Boom.’ All you kept hearing was crashing for at least 30 minutes,” Reed told The Times-Picayune/The New Orleans Advocate. She said her wife suffered injuries to her leg and side.

On social media, the National Weather Service said there were several wetland fires in the region. Smoke from the fires mixed with fog to create a “superfog.” Visibility improved as the fog lifted, according to the agency. But it was unclear how long the marsh fires, smoke from which could be seen and smelled in the New Orleans area over the weekend, would be a factor.

The Times-Picayune/The New Orleans Advocate reported several schools in and near New Orleans announced class cancellations or delayed openings due to the smoke and fog.