Schneiderman, a supporter of Trump's Democratic rival in the presidential race, Hillary Clinton, sued the real estate mogul and his now defunct Trump University for fraud in 2013, seeking $40 million in restitution plus penalties and other costs.
In a CNN interview on Tuesday, Schneiderman said his office had now brought Trump's charitable foundation under scrutiny.
"My interest in this issue really is in my capacity as regulator of nonprofits in New York state. And we have been concerned that the Trump Foundation may have engaged in some impropriety from that point of view," the elected Democratic official said.
He added: "We have been looking into the Trump Foundation to make sure it's complying with the laws that govern charities in New York." He did not elaborate on what wrongdoing Trump's nonprofit might have committed.
Trump campaign spokesman Steven Cheung dismissed Schneiderman's assertions as entirely motivated by presidential politics, calling the attorney general a "partisan hack who has turned a blind eye to the Clinton Foundation for years."
Cheung called Schneiderman's comments "nothing more than another left-wing hit job designed to distract" attention from Clinton's recent missteps on the campaign trail.