After being closed for several hours, the southbound lanes of the Lake Pontrchartrain Causeway have reopened.

A crash on the southbound span of the Lake Pontchartrain Causeway caused it to be closed Monday evening.

A garbage truck smashed into the back of an attenuator truck, shoving it over the side of the bridge and into the water, killing the driver, officials said.

Divers recovered the body of the attenuator truck driver shortly after 5 p.m., according to Carlton Dufrechou, general manager of the Greater New Orleans Expressway Commission, which operates the Causeway.

The attenuator truck was at the rear of a convoy of workers installing new signs on the southbound span. An attenuator truck, sometimes called a crash cushion truck, is built to withstand impacts and protect other members of slow-moving work convoys.

The garbage truck struck it with enough force to push it over the side of the bridge, Dufrechou said. The garbage truck then hit a police car in front of the attenuator truck, but the officer inside that car was able to get out relatively unharmed, Dufrechou said.

The wreck happened about 3:30 p.m. near mile marker 20, roughly 4 miles from the north shore, according to Jason Kaufmann, a spokesman for St. Tammany Fire District No. 4, which responded to the accident.

There were initial reports of a vehicle fire and trapped occupants, but none of those turned out to be true, Kaufmann said.

A member of the work crew jumped into the water to try to help the driver of the truck that was pushed over the side, and a Causeway worker jumped in to help pull the worker to safety, Dufrechou said. The driver of the truck did not surface.

The southbound Causeway was closed for several hours, Dufrechou said. A second closure will likely be necessary Tuesday morning while crews attempt to recover the attenuator truck, he said.

The southbound Causeway, where the concrete barriers are 6 inches lower than on the newer northbound span, has had more than a dozen overboard accidents since 1994, the majority of which have resulted in fatalities. During the same period, no vehicles have gone off the northbound span.

Causeway officials have commissioned a study by engineers at Texas A&M on ways to enhance the barriers and also have talked about the possibility of raising tolls to pay for the improvements.

Follow Faimon A. Roberts III on Twitter, @faimon.