At least 45 people were killed and more than 150 injured in a stampede at a religious festival in northern Israel, medical officials said Friday. It was one of the country’s deadliest civilian disasters.

Prime Minister Benjamin Netanyahu said children were among the dead and described it as one of the “heaviest disasters” to befall Israel, as he visited the scene.

“There were heartbreaking sights here, people crushed to death including children,” he said. “A large proportion of those who have perished have not yet been identified … This is tearing up the hearts of families.”

Video posted on social media appeared to show angry crowds jeering at Netanyahu during his visit as they blamed his government and the police for the disaster.

Netanyahu said a thorough investigation would be conducted and declared a national day of mourning on Sunday.

President Joe Biden said he had spoken with Netanyahu on Friday and offered U.S. assistance.

“The United States stands with the people of Israel, and with Jewish communities the world over, in mourning the terrible tragedy at Mount Meron,” Biden said in a statement.

“The loss of life among worshipers practicing their faith is heartbreaking.”

He added the U.S. was also “working to confirm reports that American citizens may have lost their lives or been wounded,” in the disaster.

A State Department spokesperson told NBC News “multiple U.S. citizens were among the casualties,” but did not give a specific number, adding that the U.S. Embassy in Israel was working with local authorities and providing consular support to affected U.S. citizens.

Earlier both White House national security advisor Jake Sullivan and Secretary of State Antony Blinken shared their condolences.

Read more at NBC News