A series of blasts killed at least nine people and wounded seven in the Hezbollah-controlled Bekaa Valley of eastern Lebanon on Wednesday, a security official told AFP.
Among the wounded were four Syrian workers, the official added.
Residents said the blasts hit an arms stockpile in a building under construction in an uninhabited area between the villages of Nabishit and Khodr.
Dozens of ambulances arrived at the scene as members of the Shiite Hezbollah movement surrounded the area, the residents told AFP.
The security official confirmed there had been "several explosions" but gave no immediate word on where they struck.
Hezbollah, which fought a devastating 2006 war with Israel, has a huge arsenal of tens of thousands of rockets, which it says it needs to retain in case of any new conflict with the Jewish state.
Hezbollah and its allies, which lead Lebanon's governing coalition, support Syrian President Bashar al-Assad in his 18-month battle against rebels seeking to oust him. The Lebanese opposition is bitterly opposed to the Damascus regime.