How to remove languages in transifex?

I manage a project in transifex to localize an open source C++/Qt project. A lot of people contributed translations so far and I'm satisfied with the progress made.

However, I fail to find out how to clean up unused, untranslated languages. Every now and then, people request rare languages and never contribute any translations. This produces a lot of empty translation files in my repository.

Now after a certain time I have almost 90 languages and around 20 of them are untranslated. I wonder, how can I remove them completely from my project resources?

The documentation suggests to delete the translations:

$ tx delete -r project.resource -l en_US,en_AU

I tried that, but this only removes the translations, not the language at all.

How to remove the whole language from my project?

This information is outdated, see this other answer.

Sam from the Transifex team here. You can remove languages by going to Dashboard > Teams & Languages. From there, click the down arrow next to the team that's translating your project, then hit the Delete button next to the languages you want to remove.

If you're interested, here is a diagram of the relationship between organizations, teams, projects, and languages. Hope this helps.