A major bridge over Lake Pontchartrain that was torn apart by Hurricane Katrina reopened fully to traffic just before dawn Friday.

Katrina's storm surge ripped giant sections of the five-mile concrete bridge, which links New Orleans and Slidell, La., and tossed some into the lake. Other sections of the Interstate 10 span shifted by as much as 5 feet.

Crews cannibalized undamaged sections from the westbound span to patch the eastbound lanes, which were converted temporarily to two-way traffic. That left about a mile of the westbound roadway missing, and they were replaced with a system of metal trusses and decking.

The federal government will pay about $600 million for a new, six-lane Interstate 10 bridge over Lake Pontchartrain that will replace the existing four-lane twin spans in about three years, Gov. Kathleen Blanco said Thursday during a dedication ceremony.

The rebuilt section will remain as is until it is replaced by the new bridge, state transportation officials said.

Also on Friday, the city planned to begin celebrations for Twelfth Night, the start of the Carnival season leading up to Mardi Gras.