Israeli investigators are examining what caused a crush that killed at least 45 ultra-Orthodox Jewish worshipers and injured 100 more at a mass religious gathering in Mount Meron in northern Israel.

Prime Minister Benjamin Netanyahu called the incident "a terrible disaaster,"sand said that May 2 would be declared a day of national mourning, The Times of Israel reported.

Army Radio reported that children were among the dead and injured.

By some estimates, some 100,000 people were crammed together late on April 29 to celebrate a holiday on Mount Meron, despite warnings from the authorities about the risk of COVID-19 transmission, The New York Times reported.

The deadly crush began around 1 a.m. on April 30, as celebrants began to pour out of a section of a compound hosting festivities.

The Health Ministry's death toll of 44, released later, made it one of the worst civilian disasters in Israeli history.

World Council of Churches acting general secretary Rev. Ioan Sauca expressed great sorrow on hearing the news of the loss of many lives caused by the disaster at the Lag B'Omer festival in Israel.

Sauca observed: "At such times of terrible tragedy, words may fail us, but we stand in solidarity with all those who have been affected, including the many who are mourning, and we hold them in our thoughts and prayers."

MOUNTAIN BURIAL SITE

The worshipers had crowded onto the mountain burial site to celebrate the Lag B'Omer holiday, an annual event where participants sing, dance and light fires in homage to second-century Mishnaic sage Rabbi Shim Bar Yochai.

But, in the early hours of the morning, the festival erupted into chaos, as a huge wave of people trapped others beneath them, including children, witnesses told Reuters.

"We were going to go inside for the dancing and stuff and all of the sudden we saw paramedics from MADA running by, like mid-CPR on kids, and then one after the other started coming out," said Shlomo Katz.

Early reports suggested a structure at the site had collapsed, but emergency officials later said a crush had occurred at around 1 a.m. local time, the BBC reported.

Police sources told Haaretz newspaper that it started after some attendees slipped on steps, which caused dozens more to fall.

"It happened in a split second; people just fell, trampling each other. It was a disaster," one witness told the newspaper.

Police shut down the entire event after the fatal incident and helped evacuate all the participants through the night. Roadblocks were set up to prevent people from arriving at the scene.

Earlier police struggled to clear the crowds from the scene to allow access to ambulances. Loudspeakers called in Yiddish and Hebrew for people to make way and let rescuers come through.