Landry said crews were continuing to closely monitor the rig for any more crude that might spill out.

An undetermined amount of oil was spilled from the Deepwater Horizon as it sank, appearing to cover an area about 3km wide and 13km long, Ashley Butler, a petty officer at the coast guard, said.

No blame

Karl Kleppinger Snr, whose 38-year-old son, Karl, was one of the 11 missing workers, said he did not blame the coast guard for calling off the search.

"Given the magnitude of the explosion and the fire, I don't see where you
would be able to find anything"

Karl Kleppinger Snr,
father of victim

"Given the magnitude of the explosion and the fire, I don't see where you would be able to find anything,'' he said.

Steven Newman, the CEO of Transocean Ltd, which owns the rig, said that eight of the nine missing Transocean workers were part of the crew that operated the platform's drills. The other two workers were employees of a BP contractor.

Newman said the company would continue to assist investigators in determining the cause of the blast.

The 11 missing workers came from Texas, Louisiana and Mississippi. 

The other 115 workers onboard the Deepwater Horizon semi-submersible rig at the time of the explosion on Thursday made it to safety, although 17 were airlifted to hospital after suffering injuries.

Investigation urged

Following the explosion, Bill Nelson, a US senator who has led opposition to offshore drilling, said he asked the US interior department to investigate and provide a comprehensive report on all US drilling accidents over at least the last decade.

"The tragedy off the coast of Louisiana shows we need to be asking a lot more tough questions of big oil,'' Nelson said.

"I think we need to look back over 10 years or so to see if the record denies the industry's claims about safety and technology.

An marine safety review published last year found 41 deaths and 302 injuries out of 1,443 oil-rig accidents from 2001 to 2007.

An analysis of the accidents found a lack of communication between the operator and contractors, a lack of written procedures, a failure to enforce existing procedures and other problems.

"It appears that equipment failure is rarely the primary cause of the incident or accident,'' the report said.