At least seven people were killed Monday morning after a “superfog” of smoke from south Louisiana marsh fires and dense fog caused multiple massive car crashes involving a total of 158 vehicles, authorities said.

Twenty-five people were injured and the number of fatalities may increase as first responders continue to clear the crash scenes and search for victims, Louisiana State Police said in a statement Monday evening.

Gov. John Bel Edwards issued a call for blood donors and asked for prayers “for those hurt and killed.”