"The potential impersonation of hundreds of thousands of Americans in order to influence the policy-making process should concern everyone — especially the FCC," said press secretary Amy Spitalnick.
"Yet rather than cooperate with our investigation, the commission has stonewalled it, and now offers political attacks to distract from the core issue — the manipulation of the FCC's own regulatory process," she said.
In his open letter Tuesday, Schneiderman said: "It is important that the public comment process actually enable the voices of the millions of individuals and businesses who will be affected to be heard."
But he said the FCC has essentially stonewalled his office by failing to provide evidence that is "crucial" to the investigation.
"The FCC has refused multiple requests for crucial evidence in its sole possession that is vital to permit that law enforcement investigation to proceed," Schneiderman said.
In a series of tweets on Tuesday, Schneiderman said his team has "received no substantive response" after reaching out to the FCC through a number of representatives.
Schneiderman's letter did not specify if the comments in question predominantly sought to shift the voice of the public for or against the repeal of net neutrality rules.
The state attorney general expressed his own view on net neutrality in the letter, writing, "I have long publicly advocated for strong net neutrality rules ... and studies show that the overwhelming majority of Americans who took the time to write public comments to the FCC about the issue feel the same way while a very small minority favor repeal."
But Schneiderman said the suspected scheme should concern all Americans, irrespective of their political or personal views surrounding net neutrality, on grounds that a failure to pursue illegal activity will embolden its actors in the future.
He also appeared to reference the 2016 election of President Donald Trump. Multiple U.S. intelligence agencies have said Russia interfered in the election to favor Trump.
"In an era where foreign governments have indisputably tried to use the internet and social media to influence our elections," Schneiderman said, "federal and state governments should be working together to ensure that malevolent actors cannot subvert our administrative agencies' decision-making processes."