French linux mint libreoffice missing French interface

My Linux Mint 18.2 is in French, but when I installed libreoffice 5.4.2, it is in English and the default interface does not list French, just English. However, the locale and the document language is French. How can I change to French without reinstalling everything?

  1. Install the French language pack.
  2. Set French as the interface language in the language settings dialog.