The head of the UN team investigating last February’s killing of the former Lebanese Prime Minister Rafik al Hariri says he may go to Syria to make inquiries there. UN investigator Detlev Mehlis told reporters in Beirut that without the cooperation of the Syrian authorities the investigation would not be complete. But he said he was optimistic that they would get assistance from Damascus.Four pro-Syrian Lebanese security chiefs and a politician were arrested on Tuesday in connection with the killing. Detlev also said he would need an extension to his three month term to conclude the probe. Many Lebanese believe Syrian agents were behind the bomb attack on Hariri’s cavalcade. The assassination provoked a backlash against Damascus and its influence over Lebanon. That eventually led to a withdrawal of Syrian troops from the country.