Four Israeli soldiers who were killed in southern Lebanon were likely killed in an accidental detonation of explosives as they demolished a Hezbollah tunnel laden with weapons, Israel’s Army Radio said, Reuters reports.

The Israeli military said that four soldiers fell in combat, without providing further details. Army Radio said that the incident happened on Sunday and that an initial review found that the detonation set off secondary explosions, leading to the collapse of the tunnel while the soldiers were in it.

Israeli authorities did not blame the explosion on Hezbollah or say it was a violation of the November 26 ceasefire agreement, though the two sides have accused each other of other infractions over the past two weeks.