Somali pirates have hijacked a cargo ship with 21 Americans on-board, a Kenya-based diplomat said on Wednesday. He said the 17,000-ton Maersk Alabama was taken Wednesday. Company representatives and a spokeswoman from the US embassy in Nairobi were not immediately able to confirm the hijacking. Andrew Mwangura of the East African Seafarers' Assistance Program said the ship was taken about 640 kilometers from the Somali capital, Mogadishu. The vessel is the sixth to be seized within a week and the first with an all-American crew.