Investigators in Beiruit comb through the remnants of a car bomb that killed a Lebanese intelligence officer and seven others on Friday.
Wissam al-Hassan was a well known critic of President Bashar al-Assad.
He was also a key member of a taskforce that linked Syrian forces and Hezbollah insurgents to the assassination of Lebanese Prime Minister Rafik al-Hariri.
Al-Hassan also uncovered another bomb plot that further strained tensions between the two neighbours.
Many believe the attack was a deliberate attempt to drag Lebanon into Syria's ongoing civil war.
Residents here said the bombing has left them shaken and worried about Lebanon's security situation.
SOUNDBITE) (Arabic) ASHRAFIEH RESIDENT, TAREK ZAZA, SAYING:
"Lebanon is not stable apparently, and there are no political forces uniting together, so this is really scary, and that it moves from a place to another, that is the scary part, from Ashrafieh to other towns, so God help us, we are surely scared."
The car bomb was the most serious attack in Beiruit since Hariri's death in 2005 and prompted Sunni Muslims to take to the streets in protest on Saturday.
Several roads in the capital were blocked by burning tyres as demonstrators vented their anger, while authorities beefed up security in other parts of the city.
