"Residents in Metulla reported hearing booms. We are still checking the area and haven't found anything yet," a military spokeswoman told AFP.
There was no official confirmation from Beirut, but military and security sources in southern Lebanon reported hearing the "sound of a blast", without being able to provide details on its source.
The report comes less than a day after two rockets exploded in the Hezbollah heartland of Beirut's Shiite southern suburbs, wounding four Syrian workers.
A Lebanese security source said the rockets had been fired from Aitat in the Mount Lebanon area, some 13 kilometres southeast of where they hit.