The U.N. Security Council Thursday approved an international investigation of the bombing attack on former Lebanese Prime Minister Rafiq Hariri. The 15 members of the council voted unanimously for an independent commission. The council asked the investigators to expand their work and provide a result within three months. The U.N. Secretary General Kofi Annan was authorized to extend the mandate for another three months if necessary. The Lebanese government has in principle agreed with an international investigation of the February 14 attack that killed Hariri and 19 others, and triggered unrest throughout the country as opposition supporters pointed the finger at Syria. After the attack, Syria conceded to long standing international demands that it withdraw all of its troops from Lebanon, and is expected to complete the withdrawal before Lebanon's elections in May. The investigation resolution was submitted by the United States, France and Great Britain. A U.N.-directed international inquiry has already started into the shooting, and Thursday's resolution formalizes the process into an investigation. ---SP 2236 Local Time 1936 GMT