The National Sept. 11 Memorial & Museum has received a low-interest $15 million loan from Mayor Michael Bloomberg to help the nonprofit with a budget shortfall.
The underground museum is slated to open next year.
Bloomberg is the foundation's chairman. The New York Times says he made the loan at the lowest possible interest rate of less than 0.3 percent so it would qualify as a loan rather than a gift under federal rules.
“The fact our chairman was able to extend a loan on such favorable terms is something we all recognize as something tremendously generous,” Joseph Daniels, president of the foundation told the Times.
The museum is estimated to cost around $700 million.
The foundation has received more than $425 million from the state and federal government and the Port Authority. It's also raised over $450 million in private donations.
A spokeswoman for Bloomberg didn't immediately respond to a request for comment or say why he's making a loan rather than a gift.