At least seven people were killed Monday after a “superfog” of smoke from marsh fires and dense morning fog caused a series of wrecks on Interstate 55 near New Orleans that left a long stretch of mangled and scorched cars, trucks and tractor-trailers.

An estimated 158 vehicles were involved and 25 people injured, according to the Louisiana State Police, who warned the death toll could climb as first responders worked into the night looking for victims, the smell of burnt wreckage still heavy in the air.