(CNN) -- Yemeni authorities working with the U.S. Navy intercepted a ship carrying a "substantial" cache of "illegal arms" such as surface-to-air missiles, potent explosives and rocket-propelled grenades, a U.S. official and Yemen's government said Monday. The incident took place in Yemeni territorial waters in the Arabian Sea last Wednesday, according to a statement issued five days later from Yemen's embassy in Washington.The crew of the USS Farragut, a Naval destroyer, was working with Yemeni authorities when they spotted the vessel, said an official in the Obama administration. The ship had several flags onboard, but no reliable documentation showing where...