Syria was initially the key suspect. Hariri had resisted Syria's heavy involvement in Lebanese affairs, leading to a deterioration of ties between him and Damascus in the months before his assassination. The tribunal thought that Syria had orchestrated the spectacular bombing to keep the upper hand over anti-Syrian politicians.
But investigators appeared to put the Syria file on the back burner in 2009 and began pursuing Hezbollah as more evidence emerged. The tribunal’s first indictments are widely expected to implicate Hezbollah members, though it has not given up on pursuing Syria.
Both Syria and Hezbollah have denied any involvement in the assassination.
Hezbollah has instead accused Israel of orchestrating the attack, based on confessions from alleged Lebanese spies that they were told by Israel to track Hariri’s movements and footage from Israeli reconnaissance drones that followed routes that Hariri's motorcade would take just before he was assassinated.
