New oil sightings in Gulf of Mexico

Coast guards are investigating new oil-sheen sightings on the surface of the Gulf of Mexico, which they believe could be from the sunken Deepwater Horizon oil platform.

An explosion on the rig in April 2010 triggered the worst spill in the region's history and cost the oil giant BP more than $20bn in clean-up and compensation costs.

The US Coast Guard said it suspected the oil might be coming from the debris of the rig itself, not from any leak in the plugged Macondo well on the seabed. This means that the rig operator Transocean would be financially responsible for any new clean-up, officers explained.

BP and Transocean are embroiled in a multibillion-dollar legal dispute over their respective liabilities for the disaster. Transocean has signalled that it may also try to add the costs of clearing the sheen to BP's bill.