At least seven people were killed and 36 wounded when an unmanned Israeli aircraft fired on the convoy of more than 500 vehicles.
The Israeli army confirmed it had carried out an air strike on the convoy, saying it had acted on the mistaken suspicion that Hezbollah guerrillas were smuggling weapons in the vehicles.
"The attack was carried out based on a suspicion. It was found to be incorrect," an army spokeswoman said.
The Israeli army said it had not granted permission for the convoy to travel as it was too dangerous.
The attack was near the Bekaa Valley town of Chtaura, about 50km north of the Litani River below which Israel had warned it may attack any vehicle on the roads.
The Israeli army said the convoy was on a route that is often used by Hezbollah to transport weapons to the south - the convoy was heading north.
350 Lebanese troops were
travelling wth the convoy
About 3,000 civilians and 350 Lebanese soldiers and policemen left the mainly Christian town of Marjayoun in the convoy a day after Israeli forces seized control of the area.
Witnesses said most of the victims were civilians.
One of the dead was a Red Cross worker who went to help people injured in the initial strikes.