The resources giant told US media last week that workers were removed from the platform after "anomalies" were detected in the hull.

The inspections were part of the final clearance for Neptune, 190km off Louisiana in 1300m of water, to start producing at 50,000 barrels of oil per day and 50 million cubic feet of gas per day.

Further inspection and assessment work is underway to determine any required action, co-venturer Woodside Petroleum said in a statement yesterday.

Woodside reported that the incident was likely to impact its 2008 production by 150,000 barrels of oil equivalent per month from April 1 until the issue was resolved.

Neptune is already running behind schedule and over budget.

First production was due to begin last year, while the original $US850 million development estimate was increased to more than $US1.15 billion ($A1.22 billion).

Interests in Neptune are BHP, as operator with 35%, Woodside with 20% and Marathon (30%) and Repsol (15%).