Lebanese troops raided makeshift refugee camps near a predominantly Christian village on the border with Syria on Tuesday a day after two waves of suicide attacks.
But Interior Minister Nuhad Mashnuq said the attackers who carried out Monday's violence had come from inside Syria, not refugee settlements nearby.
"We are worried that there are more terrorists, so the Lebanese army is searching the area," said Bashir Matar, mayor of Al-Qaa, which lies in a hilly border area shaken by violence since the civil war erupted in Syria in 2011.
Five people main road linking the Syrian town of Al-Qusayr to Lebanon's eastern Bekaa valley.
Its 3,000 residents are predominantly Christian, but the Masharia Al-Qaa district is home to Sunni Muslims and some 30,000 Syrian refugees live in a makeshift camp were killed and 15 wounded when four suicide bombers attacked the village before dawn on Monday.
A second wave of attacks hit Al-Qaa on Monday night. Another four suicide bombers wounded 13 people.
Al-Qaa lies on a on the edge of the village.
"The army has deployed a large force to Masharia Al-Qaa and is carrying out widespread searches in the displacement camps, looking for weapons or wanted people," the state National News Agency reported.
In televised comments from Al-Qaa on Tuesday, the interior minister said a preliminary investigation indicated that "the suicide attackers came from Syria, not from the (refugee) tents."
Residents also took to the streets with their own weapons in an apparent show of force, an AFP journalist reported.
"The whole village is mobilising. Everyone -- men and women -- are sitting in front of their homes to protect them after the terror that we lived yesterday," said local official Mansur Saad.
One man with silver-grey hair and clad in a black vest poured himself a small cup of coffee, his assault rifle lying in his lap.
Several women strolled through the street and posed in front of cameras, smiling and gingerly carrying weapons.
"We haven't been scared or terrified like that in our whole lives," said resident Yola Saad.
"All the guys from the village came out with their guns to protect their neighbourhoods," she added.
Prime Minister Tamam Salam urged residents not to take up arms and to leave the military work to the security forces.
In Baalbek, an eastern city known for its ancient ruins, soldiers "carried out raids in the refugee camp... and arrested 103 Syrians who were on Lebanese territory illegally," an army statement said.
Lebanon is host to more than one million Syrian refugees, roughly a quarter of the small Mediterranean country's population.
Lebanese Shiite movement Hezbollah, which has sent thousands of fighters to Syria to back President Bashar al-Assad, has set up informal checkpoints along the road to Baalbek area "to search cars," a Hezbollah official told AFP.
There was no immediate claim of responsibility for Monday's attacks which bore the hallmarks of jihadist organisations like the Islamic State group or Al-Qaeda.
Suicide blasts in the area have typically targeted checkpoints or military installations and rarely included more than one attacker.
In August 2014, the army clashed with the IS and Al-Nusra Front, Al-Qaeda's affiliate in Syria, in the border town of Arsal.