Federal and city prosecutors are investigating a $52M deal to build a luxury condo tower on top of the Brooklyn Heights public library branch, over allegations the project was awarded to a longtime friend of Mayor Bill de Blasio who submitted a bid to pay the city less than others during the RFP process.

The new investigation adds a seventh pay-to-play scandal to the de Blasio Administration’s plate, the New York Post reports. In the deal, Hudson Cos was chosen to develop a 30-story condo on top of the library, despite allegedly submitting a bid that was $6M less than a competing firm, and included slightly less affordable housing.

Hudson’s David Kramer proposed paying the city $52M for the project, and included 114 units of affordable housing at a nearby site.

The Post reports at least two other firms offered more money and to build more affordable units—or to build them on-site—than Hudson. Brooklyn-based Second Development Services, for example, offered $6M more, along with 117 affordable units. Kramer has been a personal friend of de Blasio for over a decade, and has given roughly $9k to his various campaigns since 2007.

The offices of US Attorney Preet Bharara and Manhattan District Attorney Cyrus Vance have sent subpoenas to several of the 14 developers who bid on the project, sources tell the Post. [NYP]