Seven people dead in pileup on a Louisiana highway

ST. JOHN THE BAPTIST PARISH, Loui. (NBC, KYMA/KECY) - Cleanup is underway after Monday's fatal pileup on a Louisiana highway.

Drone video shows the extent of the damage still left behind.

At least seven people were killed and 30 others injured in the massive pileup. At least two 18-wheelers erupted into flames.

Cars and trucks were stacked on top of each other, and one vehicle was pushed over the railing and into the water below the interstate.

Louisiana State Police said the number of fatalities may increase as first responders continue to clear the crash scene and search for victims.

Authorities say the cause of the pileup was largely due to a combination of dense fog and smoke from nearby wildfires that, when combined, creates a phenomenon called a "super fog," reducing visibility to near zero.