NEW ORLEANS (AP) — Crews worked into Tuesday morning clearing the wreckage of more than 150 vehicles involved in a series of crashes the day before on Interstate 55 near New Orleans caused by a “superfog” of marsh fire smoke and dense fog that killed at least seven people and injured another 25.

Hazardous driving conditions Tuesday morning prompted several schools in the area to close or delay.

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

The crashes began before 9 a.m. Monday and there were several crashes along a one-mile span of the highway, Louisiana State Police Sgt. Kate Stegall said in a news briefing. The highway was expected to remain closed at least until the bridge could be inspected for damage in daylight Tuesday, Stegall said.

The crashes left a long stretch of mangled and scorched cars, trucks and tractor-trailers. Vehicles were crushed, piled atop each other and engulfed by flames. Some people got out of their vehicles and stood on the side of the road or on the roofs of their cars looking in disbelief at the disaster, while others cried out for help.

Clarencia Patterson Reed was driving with her wife and niece and could see people waving their hands for her to stop, but when she did her car was hit from behind and on the side by two other vehicles, she told the The Times-Picayune/The New Orleans Advocate.

“It was ‘Boom. Boom.’ All you kept hearing was crashing,” Reed said. She was able to scramble out of her car, but her wife was pinned inside and injured her leg and side.

Another driver Christopher Coll, said he was already braking when a pickup truck “drove up on top of my work trailer and took me for a ride.”

Coll could smell smoke as he heard the sounds of crashing cars and popping tires. He was able to kick open his passenger door to escape and then helped others — pulling out one person through a car window.

While 25 people were brought to the hospital, with injuries ranging from minor to critical, others sought medical aid on their own, authorities said.

Louisiana Gov. John Bel Edwards asked for prayers “for those hurt and killed” Monday and issued a call for blood donors to replenish dwindling supplies.

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 (39-kilometer) 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.