A US military commander has determined that Marines accused of killing civilians after a suicide bombing in Afghanistan last month used excessive force, and he has referred the case for possible criminal inquiry, The Associated Press has learned. The initial investigation of the March 4 incident, in which up to a dozen Afghan civilians are reported to have died, concluded that the Marines' response was "out of proportion to the threat that was immediately there," a senior defense official said Wednesday. The official spoke on condition of anonymity because the probe's results have not been released. The findings have been forwarded to Central Command, which has responsibility for US military operations in the Middle East and Central Asia. The case has also been referred to the Naval Criminal Investigative Service for a broader criminal inquiry, the official said.