Claims of antisemitism are being made by travelers from a Lufthansa flight that originated out of New York’s John F. Kennedy International Airport, CBS New York reports.

Multiple Jewish organizations claim more than 100 Jewish passengers weren’t allowed to go on a connecting flight from Frankfort to Budapest due to a mask dispute.

People on the flight last Wednesday claim several Orthodox Jews refused to wear a mask, which the carrier still requires. But instead of just excluding those men, the airline allegedly didn’t allow any visibly Jewish person to continue their trips.

In a statement, the airline acknowledged denying boarding to a large number of people and said it regrets the circumstances surrounding the event. The decision, it said, “resulted from multiple incidents of non-compliance with crew safety instructions, including not wearing masks.”

Lufthansa said it’s still reviewing what happened and it apologizes to the passengers, adding that it has “zero tolerance for racism, antisemitism and discrimination of any type.”