UPDATE - The northbound lanes of the Lake Pontchartrain Causeway have reopened.

LaPLACE — Heavy fog forced the closure of two major thoroughfares in southeastern Louisiana on Tuesday. The Lake Pontchartrain Causeway was shut down for hours after several traffic crashes and the Interstate 10 bridge over the Bonnet Carre Spillway was closed temporarily to accommodate periods of low visibility.

Carlton Dufrechou, the general manager of the Lake Pontchartrain Causeway, said there were six crashes -- two on the southbound span and four on the northbound span. At least 11 people were transported to area hospitals, according to WWLTV.

The WBRZ Storm Team says weather conditions have been ripe for morning fog, and additional foggy weather is possible Wednesday morning. Conditions should change after a cold front arrives in the second half of the week.

Along I-10, traffic leaving New Orleans was diverted just past the Louis Armstrong International Airport, while eastbound traffic was diverted at LaPlace. Highway crews reopened all lanes of I-10 about 10:45 a.m.

The causeway, meanwhile, was closed for hours after a number of crashes were reported before 9 a.m. 

The causeway's operators said 11 cars were involved in fog-related crashes, but there were reports that up to 40 or 50 vehicles were involved. The higher numbers could not be confirmed immediately.

The National Weather Service overnight had issued a dense fog advisory for the lake and other points in coastal Louisiana, saying visibility would be reduced to a mile or less.

Last year, a "super fog" event that included smoke and fog led to a 168-vehicle crash on Interstate 55, which is located about 18 miles west of the causeway. Those crashes left seven dead.