Two US offshore production platforms in the Gulf of Mexico have been shut down and a third was evacuated as a precaution after a giant oil spill and further shutdowns are possible, the US Minerals Management Service said on Saturday.

The MMS statement was the first sign that the spill has affected US offshore energy production, even though the three platforms account for less than 0.1 percent of daily Gulf of Mexico output.

Some 6.2 million cubic feet per day of natural gas production is shut down, the service said. The Gulf provides 25 per cent of US oil output and 15 percent of US natural gas production.

The MMS said it would not identify the names or companies that own the affected platforms, but said more platform shutdowns are likely as the spill spreads eastward.

'Yes, there's always the possibility of that,' MMS spokeswoman Eileen Angelico said, when asked if additional shutdowns were possible.

The rig Deepwater Horizon, owned by Transocean Ltd, sank on April 22, two days after it exploded and caught fire while finishing a well for BP 42 miles off the Louisiana coast.

The companies and the US government are in the process of trying to seal the leaking oil well. On Monday, an offshore drilling rig owned by Diamond Offshore Drilling Inc that had been working near a sunken rig was evacuated as a precaution, an MMS official said.

The last event to affect offshore production was hurricanes Ike and Gustav in 2008, which shut down nearly all the region's output for weeks.-Reuters