JERUSALEM, May 1 (Reuters) - U.S. citizens are among the dozens killed and injured in a stampede at a religious festival in Israel, the U.S. Embassy said on Saturday, as criticism mounted in the wake of one of the biggest civilian disasters in the country's history.

At least 45 people were crushed to death and more than 100 injured at the ultra-Orthodox Jewish festival on the slopes of Israel's Mount Meron, held overnight between Thursday and Friday.

The exact cause of the disaster is still not clear but witness accounts and videos posted on social media suggested that some people had fallen down stairs leading out of a narrow passageway packed by hundreds of worshippers trying to exit the site, as a surge of people came down upon those ahead of them who had fallen, being trampled and asphyxiated.

One witness described seeing a pyramid of people piling up one on top of the other. Authorities said there were children among those hurt.

The Health Ministry said 42 of the dead had been identified by late Friday. The identification process paused for 24 hours in observance of the Jewish Sabbath, resuming on Saturday evening.

Newsletter signup for email alerts

More than 20 of the people injured were still in hospital by Friday night. More than 2,000 Israelis across the country responded to an emergency call for blood donations, according to Magen David Adom, Israel's ambulance service.

A U.S. Embassy spokesperson said: "We can confirm that multiple U.S. citizens were among the casualties."

Those included both dead and injured. The U.S. Embassy was trying to verify if any more U.S. citizens were involved and is providing all possible consular support to affected U.S. citizens, the spokesperson said, declining to comment further.

The Israeli Foreign Ministry said on Friday that consulate officials in New York were in contact with four families of victims and the Israeli embassy in Argentina was in contact with one family.

U.S. media have identified some of the dead, including a 19-year-old American citizen who was in Israel on a gap year.

Canadian Prime Minister Justin Trudeau said on Friday that two Canadians were killed in the disaster.

The Justice Ministry said investigators would look into whether there had been any police misconduct connected to the tragedy and that police had started their own investigation into the incident.

There had been concern for years about safety risks at the annual event, held at the tomb of a 2nd-century Jewish sage in the Galilee.

Anger has mounted at the government and the police for allowing the event to go ahead despite its size far exceeding the coronavirus restrictions on gatherings. An estimated 100,000 packed the festival.

Some critics said politicians had caved to pressures of ultra-Orthodox leaders who are presently allied with Prime Minister Benjamin Netanyahu but have flouted the state's authority for years.

"The government wouldn't consider any restrictions for fear of its Haredi (ultra-Orthodox) partners. And as far as physical safety was concerned, this year wasn’t any different from previous ones. Warnings of a potential disaster have been heard many times before, including from members of the Haredi community, but the traditions must not be changed," wrote Anshel Pfeffer, an analyst for the left-wing Haaretz newspaper.

(Reporting by Maayan Lubell, editing by Angus MacSwan)