A second oil platform of British Petroleum is reported to have sunk into the waters of the Gulf of Mexico thus causing an even larger ecological disaster.

The BP rig went under water while being transported to a scrap warehouse nearby Morgan City in the US state of Louisiana.

There are no casualties in Saturday's rig incident and shipping has not been hampered in the Louisiana navigation channel. US authorities have explained that about 200 gallons of oil have spilled in the incident. A foaling barrage has already been installed to contain the slick.

Up to 5 000 barrels of oil a day are thought to be spilling into the water after last week's explosion on a BP-operated rig, which then sank, the BBC reported.

The sprawling oil slick has begun washing up on the Louisiana coast and is threatening three other states.

The US states of Mississippi and Alabama to join Louisiana and Florida in declaring a state of emergency and have triggered US authorities to pressure the British oil giant into taking immediate measures to tackle the oil spill.

Louisiana state authorities have decided to send inmates to help cleanse the Gulf of Mexico.

Worsening weather conditions have been hampering efforts to contain the slick, which is more than 200km long.

Weather forecasters predict that strong winds could push the oil into inlets, ponds and lakes in south-east Louisiana over the weekend.

Animal rescue groups have been receiving their first patients - seabirds coated in oil.

The US navy has also been deployed to help avert a looming environmental disaster.

The US Coast Guard reported late on Thursday that long, thin traces of crude oil were washing up on the Louisiana shoreline.

Thicker concentrations were a few miles offshore.

The US government has designated the Gulf of Mexico oil spill as an "incident of national significance". This allows it to draw on resources from across the country to deal with the leak.