The traffic on Mississippi River was flowing again Saturday, but it is still limited, as officials are working to clean up the worst oil spill at New Orleans in nearly ten years.

The U.S. Coast Guard began allowing some traffic to pass down the river Friday, and assured that the effects of the big oil spill were limited by “booms,” absorbent collection rings which were placed north of the Mississippi delta wetlands, The New Orleans Times Picayune reported.

Traffic was partially allowed due to the economic importance of the ships’ cargo. The spill that caused Mississippi River to close at New Orleans is costing the U.S. economy $275 million a day, the head of that city’s port authority told CNN.

New Orleans mayor Ray Nagin Friday said the Algiers community’s water supply was not endangered by the oil spill. He told a newspaper that an independent testing company found that the Algiers’ water intake system was not contaminated with oil.

The spill happened due to a collision Wednesday between a 600-foot tanker and a tugboat pushing one barge.

No injuries were reported, but the incident caused more than 419,000 of the heavy, strong-smelling fuel to spill into the river. Mississippi was closed 45 minutes after someone reported a strong diesel odor coming from the water.