ANCHORAGE, Alaska (AP) — More than a dozen Alaska Native and environmental organizations have sued to block offshore oil drilling in the Beaufort Sea off Alaska's north coast.The 13 groups on Thursday filed the legal challenge to federal approval in August of Shell Oil's exploration drilling plan.Earthjustice attorney Holly Harris says in a statement that allowing Shell to drill when it has no credible plan to clean up an Arctic Ocean oil spill is insulting and irresponsible.Shell's exploration plans calls for drilling up to three exploratory wells in the Chukchi (CHUCK'-chee) Sea and two in the Beaufort Sea in 2012.The company claims the chance of a spill during exploration is minimal and that its spill response plan, which includes a fleet of response vessels, meets federal requirements.