Shares in BP fell after the oil giant that is still reeling from last year's spill in the Gulf of Mexico shut down a major oil pipeline in Alaska due to a leak.The pipeline is responsible for about 12% of the US's total crude oil output.BP was one of the heaviest fallers in the FTSE 100 after the news, but other oil groups such as Shell were higher as concerns over possible disruption helped push up the oil price.The leak on the Trans-Alaska pipeline, which serves the US's largest oil reserve Prudhoe Bay, was discovered on Saturday. It has not yet disrupted shipments or caused any known environmental damage.A spokesman from Alyeska Pipeline Service, which operates the pipeline and is 47% owned by BP, said: "Our goal is to engineer and implement a solution so that we can safely return the pipeline to service as quickly as possible."