Yasser Ataya, mayor of the southern Lebanese village of Teir Harfa, told The Daily Star newspaper that a rocket from the 2006 war between Hezbollah and Israel exploded, though there were no reports of casualties.
Andrea Tenenti, a spokesman for the U.N. Interim Force in Lebanon, told the newspaper that peacekeepers deployed to the scene alongside the Lebanese military.
"We are trying to ascertain the nature of the place and the nature of the explosion," he said.
Hezbollah security forces reportedly sealed the area shortly after the explosion Monday morning.
The Lebanese newspaper said Israel jets were seen flying over the area after the blast. A peace deal that helped secure a peace deal between Hezbollah and Israel calls on the Shiite group to lay down its weapons while reminding Israeli of its obligation to respect Lebanon's sovereignty.