Around 20 people, including children and teachers, were injured in an explosion near Israel’s border with Lebanon on Monday, with authorities investigating whether an unexploded munition caused the blast.

According to Magen David Adom (MDA), one person is in critical condition, two are seriously injured and three are in moderate condition. Approximately 15 others are reported to be in good condition.

The group was near the Pe’er observation point, close to Kiryat Shmona in the Upper Galilee, when the explosion occurred.

Prime Minister Benjamin Netanyahu has been briefed on the incident and discussed the situation with MDA Director General Eli Bin, Education Minister Yoav Kisch and his military secretary.

The exact cause of the explosion remains under investigation.