The weapons and chemicals came from North Korea and did not appear on the ship's manifest, which showed only that the merchant vessel was carrying bags of cement. After intercepting the freighter, Spain then handed the ship over to the US Navy. Immediate official explanations out of Washington and Madrid said the missiles might have been headed for the al-Qaeda network, which the US government holds responsible for the September 11, 2001, terrorist attacks in New York and Washington. However, just hours later, the US administration took Spain by surprise by turning the So San over to Yemen, explaining that the cargo was actually a legal shipment of weapons purchased from North Korea by the Yemini government.

The handover was preceded by a telephone conversation between US Vice President Dick Cheney and Yemeni President Ali Abdullah Saleh. When that conversation was made public, the White House justified the move by calling Yemen a friendly nation. So what initially came off as a brilliant Spanish military operation to prevent illegal trade in weapons of mass destruction was reduced to a suspected manipulation directed from Washington, with Madrid in the role of receiving and carrying out orders that were not very clear in their purpose.