CNN Business  — 

Facebook is trying to scuttle the work of New York University researchers who have played an important role in bringing attention to the company’s political ad-targeting practices.

The researchers collect information about what sorts of political ads that American voters see on the platform.

Facebook (FB) demanded in an October 16 letter that the researchers stop collecting Facebook (FB) data through a tool NYU developed to track political ads. The letter, signed by Allison Hendrix from the company’s privacy and data policy team, also demanded the researchers delete all data they have gathered through the tool.

Laura Edelson, a Ph.D. candidate in computer science at NYU and the lead researcher behind the project, said in a statement Friday evening that her team had built a tool that provides an analysis of political advertisers’ and Facebook’s practices “that is otherwise unavailable to the public, and which makes clear who is trying to influence us and why.”

The tool allows Facebook users to voluntarily share their data with the NYU researchers.

Facebook’s vast data collection on its users allows advertisers “to profile citizens and send them misinformation about candidates and policies that are designed to influence or even suppress their vote,” said NYU professor Damon McCoy. “Shutting down a key data source for studying election interference and manipulation—in November, of all months—impedes our efforts to safeguard the democratic process.”

Joe Osborne, a Facebook spokesperson, said Friday the company told NYU “months ago” that building a tool like this violates the company’s terms of service.

Facebook has rules that restrict how third party tools can be used to collect Facebook data.

Osborne pointed out that Facebook has built its own tools for the public and for researchers to access information about political ads.

NYU also uses some of Facebook’s tools in its research.