The US state of Louisiana has called for emergency aid as a giant oil slick from a sunken rig in the Gulf of Mexico is approaching its coast. Governor Bobby Jindal said a change in wind direction means the slick could reach the coast as early as Thursday - and damage its fragile eco-system. The oil rig sank last week after a deadly explosion killing eleven workers. The US Coast guard says oil is pouring out at the rate of 5000 barrels a day - than fives more than previously estimated.