BEIRUT (AP) — An explosion has rocked a Hezbollah stronghold in southern Lebanon, sending thick grey smoke billowing over the village, but the cause was not clear. The blast occurred in the southern village of Ain Qana, above the port city of Sidon. There were no immediate reports of casualties. The explosion occurred in a Hezbollah arms depot in the village, one Lebanese security official in south Lebanon said, without elaborating on the cause. An official with the Shiite militant group confirmed there was an explosion but declined to give further details.