Italy risks its worst environmental disaster in more than two decades if the 2,400 tonnes of thick fuel in the capsized Costa Concordia pollutes one of the Mediterranean's most prized and pristine maritime reserves. Seven days after the 114,500 tonne liner capsized off the Tuscan coast, its vast wreck is shifting precariously on an undersea ledge, threatening to slide further and undermining plans to pump the oil out safely. The ship keeled over after striking a rock and is now lying on its side on a shelf in about 20 meters of water off the little island of Giglio. Eleven people were killed and 21 are still unaccounted for. With hopes of finding any survivors all but gone, experts warn that beyond the loss of lives, this could turn into Italy's worst maritime environmental emergency since the sinking of the Amoco Milford Haven, loaded with 144,000 tonnes of oil, off the coast of Genoa in 1991. The clean up of that area was completed in 2008, 17 years after the accident, and the Haven shipwreck is still on the seabed, said Luigi Alcaro, head of maritime emergencies at ISPRA, Italy's government agency for the environment.