An offshore drilling company has stopped the discharge of oil from a platform it owns in the US Gulf a week after Hurricane Ida brought extensive damage to the coast of Louisiana.

The US Coast Guard (USCG) on Sunday identified during an aerial investigation over Bay Marchand off Port Fourchon that a wellhead to S2 Energy's Enterprise offshore drilling rig had been discharging oil.

S2 Energy has since reported that it has stopped the discharge, which left an oil swathe that was 91.4 meters long by 91.4 metres wide, after securing the wellhead.

Members of the National Strike Force aboard a USCG aeroplane "observed no active discharge at the Bay Marchand site or near the Enterprise site", the USCG said.

S2 Energy has contracted an oil spill response organisation to boom the area, mitigate the spread of oil and clean up the spill.

"Estimates of release are yet to be determined" but an oil sheen as long as 8 kilometres have been observed, the USCG said.

The USCG said it is handling almost 350 reported incidents related to the hurricane that state, local, and federal authorities will further investigate.

Recovery underway

Tanker and bulker markets in the storm-impacted area are still struggling to restore operations as of Monday.

The USCG over the weekend reopened the Lower Mississippi River to all vessel traffic in New Orleans and key ports throughout southeastern Louisiana.

The waterway was opened to marine traffic after the removal of downed transmission tower power lines and survey of the ship channel.

The USCG is working to return southeastern Louisiana's ports in Fourchon, Bayou Lafourche and Houma Navigation Canal and the Gulf Intracoastal Waterway to pre-storm capacity.

Vessel movement and cargo operations are authorised with restrictions on speed and tow sizes.

Hurricane Ida caused historic disruptions to Louisiana refinery operations, which export about 700,000 barrels per day of clean petroleum products.

Since the hurricane hit Louisiana a week ago, the Baltic Clean Tanker Index has fallen steadily to 507 points from 543 points.