Update, 9:25 a.m. Thursday:

All southbound lanes on the Lake Pontchartrain Cause Bridge are now open.

Original story:

An accident on the Lake Pontchartrain Causeway Bridge has shut down southbound traffic Thursday morning.

Alternate routes are I-55 southbound or I-10 westbound.

State officials announced the closure of the southbound lanes around 7:10 a.m. It wasn't immediately clear when the lanes would reopen.