A stampede broke out early Friday at a Jewish religious gathering attended by tens of thousands of people in northern Israel, leaving 150 hospitalized, authorities said. Israeli media reported that as many as 44 people were killed and published photos of rows of bodies.

The disaster occurred at Mount Meron at the main celebrations of Lag BaOmer, a holiday when tens of thousands of people, mostly ultra-Orthodox Jews, gather to honor Rabbi Shimon Bar Yochai, a 2nd-century sage and mystic who is buried there. Large crowds traditionally light bonfires, pray and dance as part of the celebrations.

Prime Minister Benjamin Netanyahu called it a “great tragedy,” and said everyone was praying for the victims.

The incident happened after midnight, and the cause of the stampede was not immediately clear. Videos circulating on social media showed large numbers of ultra-Orthodox Jews packed together in tight spaces.

A 24-year-old witness, identified only by his first name Dvir, told the Army Radio station that “masses of people were pushed into the same corner and a vortex was created.” He said the first row of people fell down, and then a second row, where he was standing, also began to fall down from the pressure of the stampede.

“I felt like I was about to die,” he said.

Zaki Heller, spokesman for the Magen David Adom rescue service, said 150 people had been hospitalized and confirmed there had been some deaths. Army Radio, citing anonymous medical officials, said the death toll had risen to 44.

Heller told the station “no one had ever dreamed” something like this could happen. “In one moment, we went from a happy event to an immense tragedy,” he said.

Photos from the scene showed rows of wrapped bodies.

The Israeli military said it had dispatched medics and search and rescue teams along with helicopters to assist with a “mass casualty incident" in the area. It did not provide details on the nature of the disaster.

It was the first huge religious gathering to be held legally since Israel lifted nearly all restrictions related to the coronavirus pandemic. The country has seen cases plummet since launching one of the world's most successful vaccination campaigns late last year.

Health authorities had nevertheless warned against holding such a large gathering.

But when the celebrations started, the Public Security Minister Amir Ohana, police chief Yaakov Shabtai and other top officials visited the event and met with police, who had deployed 5,000 extra forces to maintain order.

Ohana, a close ally of Netanyahu, thanked police for their hard work and dedication “for protecting the well-being and security for the many participants” as he wished the country a happy holiday.

Netanyahu is struggling to form a governing coalition ahead of a Tuesday deadline, and the national tragedy is sure to complicate those efforts.