A knifeman attacked a Hanukkah celebration at a rabbi's home north of New York City late on Saturday, stabbing and injuring five people before fleeing in a vehicle, police said.
The attack appeared to be the latest in a string targeting Jews in the region, including a massacre at a kosher grocery store in New Jersey earlier this month.
Police said the stabbings happened at around 10pm in Monsey, one of several Hudson Valley towns that have seen an influx in large numbers of Hasidic Jews in recent years.
Ramapo Police Chief Brad Weidel said hours later that New York City police had located a vehicle and possible suspect being sought in connection with the stabbing.
New York City Police would not immediately confirm whether anyone was in custody.
Top state officials, including Governor Andrew Cuomo and Attorney General Letitia James, released statements condemning the attack.
Photos and videos posted on Twitter showed a large emergency response with paramedics running and pushing stretchers. A number of police and emergency vehicles could be seen in the images.
The Anti-Defamation League of New York and New Jersey said it was also aware of the reports and was at the scene in Monsey.
Monsey is about an hour north of New York City.
The Orthodox Jewish Public Affairs Council for the Hudson Valley region tweeted reports that the stabbings took place at the house of a Hasidic rabbi while they were celebrating Hanukkah.
Several state and local officials described the location of the stabbing as a synagogue. The rabbi's home is next door to a synagogue.
Saturday was the seventh night of Hanukkah.
Governor Cuomo, who called the stabbings a "cowardly act", has directed the state police hate crimes task force to investigate the attacks.
"Let me be clear: anti-Semitism and bigotry of any kind are repugnant to our values of inclusion and diversity and we have absolutely zero tolerance for such acts of hate," he said.
"In New York we will always stand up and say with one voice to anyone who wishes to divide and spread fear: you do not represent New York and your actions will not go unpunished."
Police chief Mr Weidel said the five people were taken to hospital for treatment, but the extent of their injuries was not clear.
Authorities have not provided a motive for the attack.
The incident happened a month after a man needed surgery after being stabbed while walking to a synagogue in Monsey. It is not known if anyone has been arrested for that attack.
Jewish communities in the New York City metro area have been troubled following a deadly gun rampage at a northern New Jersey kosher market on December 10.
Six people died in the shooting, including the two killers, a police officer and three people who had been inside the store. New Jersey Attorney General Gurbir Grewal said the attack was driven by hatred of Jews and law enforcement.
Around New York City, police have received at least six reports this week – and eight since December 13 – of attacks possibly prompted by anti-Jewish sentiment.
Mayor Bill de Blasio said on Friday that the police presence would be increased in Brooklyn neighbourhoods with large Jewish populations.