Today in a short blog post, Slack announced that it had removed 28 accounts with a “clear affiliation with known hate groups.” Few details were provided about the accounts or how Slack identified them, but we have reached out to the company for more information.

The announcement, brief as it is, comes as a surprise. To date, Slack has managed to stay out of the conversation around what happens when sometimes violent politically extreme organizations use popular social platforms to organize. While that conversation should be fairly clear-cut when it comes to public-facing content somewhere like Facebook, it’s a bit more nuanced on messaging platforms where communication is private in nature.

Slack is mostly used for workplace communication, but the chat platform Discord, popular with gamers, has been grappling with the same issues. In 2017, Discord removed a public server tied to AltRight.com that the company said violated its rules against harassment and calls for violence. As fringe groups are booted off of mainstream platforms, it will be interesting to see where they wind up and how their new platforms of choice will handle their unsavory new clusters of users.

For reference, here’s Slack’s full blog post:

Today we removed 28 accounts because of their clear affiliation with known hate groups. The use of Slack by hate groups runs counter to everything we believe in at Slack and is not welcome on our platform. Slack is designed to help businesses communicate better and more collaboratively so people can do their best work. Using Slack to encourage or incite hatred and violence against groups or individuals because of who they are is antithetical to our values and the very purpose of Slack. When we are made aware of an organization using Slack for illegal, harmful, or other prohibited purposes, we will investigate and take appropriate action and we are updating our terms of service to make that more explicit.

Update: A Slack spokesperson declined to offer additional details but provided the following statement. “We don’t normally comment on how we conduct our investigations, but we want to be clear that the privacy of our customer data is sacrosanct,” the Slack representative said. “In this case, we were informed of the possible use of Slack by hate groups and we were able to determine their affiliation on an organizational level.”