A scandal within the New York Police Department, which led to four arrests Monday, has its roots within an investigation into Mayor Bill de Blasio’s fundraising.

The four officers were arrested Monday on corruption charges, including accepting gifts for favors. At the center of this controversy are two businessmen, Jeremiah Reichberg and Jona Rechnitz, who just happen to be major campaign donors for de Blasio.

The two men have for years allegedly tried to increase their political influence in the city and use the police department for their own personal interests, including using officers as chauffeurs or bodyguards. Federal authorities, who are investigating de Blasio’s many fundraising efforts, uncovered just how far the two businessmen’s reach had gotten throughout the city.

Investigators found that four officers—Deputy Chief Michael Harrington, Deputy Inspector James Grant, Officer Richard Ochetal, and Sergeant David Villanueva—had accepted more than $100,000 in gifts from the two businessmen. The New York Times reported Monday:

The court papers in the case detail lavish gifts the two senior police officials are accused of receiving in exchange for taking official action, including expensive meals and free overseas and domestic trips; and the referral of business to a security company associated with one of the officials. The deputy inspector was also accused of receiving a trip on a private jet to Las Vegas for the Super Bowl weekend in 2013, accompanied by a prostitute. The sergeant was charged in a separate but related scheme that involved aiding applicants for firearms licenses, the papers said.

Reichberg was charged along with the four officers. Rechnitz, the other businessman, recently pleaded guilty to corruption charges for allegedly bribing the head of the union that represents the city’s corrections officers as well as a hedge-fund financier, and has started cooperating with investigators.