Emergency rescue workers struggled to save lives when dozens died and hundreds were injured during the annual Lag b’Omer festivities in the northern Israeli town.

At least 45 people died and more than 100 were injured, some critically, Thursday night in the northern Israeli town of Meron, where hundreds of thousands celebrated the holiday of Lag b’Omer, visiting the gravesite of 2nd-century sage Rabbi Shimon Bar-Yochai.

Authorities are investigating the cause, but it appears it was the result of a slippery staircase.