Multiple Americans were among those killed and injured in a stampede in Israel that's killed dozens, the State Department said Friday.
The State Department has not released the number of Americans involved, but the Consulate General of Israel in New York said four of the 45 people reported dead were American citizens.
Among the Americans killed was 19-year-old Daniel "Donny" Morris of Bergenfield, New Jersey, said his uncle, Rabbi Yechiel Morris.
He said his nephew was studying in Israel for the year on a gap program.
"We are all shocked and devastated," Yechiel Morris said. "There are no words."
Other American victims included Yosef Amram Tauber, 18, of Monsey, New York; Eliezer Josef, 26, of Kiryas Joel, New York; and Shraga Gestetner, 33, of Monsey, New York. Gestetner was originally from Montreal.
"Our Embassy and Department of State will provide all necessary support to any U.S. citizens and their family members affected," President Joe Biden said earlier on Friday.
In addition to those killed, at least 150 others were hospitalized -- nearly two dozen in critical condition -- after the stampede around midnight Friday at Mount Meron during Lag BaOmer festivities, according to the Israeli Health Ministry.
"The Meron disaster is one of the worst disasters in the history of Israel. We mourn the dead, our hearts go out to the families of those wounded, to them we wish a full recovery," Prime Ministry Benjamin Netanyahu said in a statement Friday.
"We have seen here heart-breaking sights, people who were crushed to death, including children," he said. "A large number of the fatalities have not yet been identified."
"I have to point out here the speedy rescue effort of the police and the other security and rescue organizations, we are grateful to them. Their work prevented an even larger disaster," he continued. "We will conduct a thorough investigation so such a disaster will not happen again."
The MDA said helicopters were sent to work with ambulances to bring victims to Ziv Hospital in Safed and Galil Medical Center in Nahariya.
Lag BaOmer is an annual celebration on the anniversary of the death of Rabbi Shimon bar Yochai, a 2nd century sage who was buried in a tomb at Mount Meron in northern Israel. The festivities include pilgrimages to bar Yochai's tomb and lighting bonfires and celebrating throughout the night.
Netanyahu declared Sunday a national day of mourning.
Biden said he spoke with Netanyahu to offer his "profound condolences" and said the U.S. was offering assistance to Israel.
"Our prayers are with those who were injured and all those who lost loved ones," Biden said. "May their memories be a blessing."
ABC News' Bruno Nota, Molly Nagle, Christine Theodorou, Aaron Katersky and Rashid Haddou contributed to this report.