NEW ORLEANS (AP) – A large fuel spill that shut down the mouth of the Mississippi River for four days has had a limited impact on wildlife so far, but officials are worried about fragile wetlands downstream.

A tanker and a barge collided early Wednesday, spilling about 419,000 gallons of fuel oil from the barge, closing the river from New Orleans to the Gulf of Mexico and temporarily idling some 200 ships.

Officials said they had reports of only limited impact on stretches of the winding river fronted by levees topped with rocky cover, concrete mats and other anti-erosion materials. But MacKenzie cautioned that canvassing such a vast area was a tall challenge and probably only a fraction of the affected wildlife had been spotted.

Roland Guidry, a state official coordinating the cleanup, said the oil may never reach wetlands including the federal Delta National Wildlife Refuge and the state’s Pass-a-Loutre Wildlife Management Area.

Currents could push it to the banks before it gets that far.

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