** Updated: 27 September 2016 11.15am **
Facebook have deployed a fix and we have reports from a number of customers and staff that it appears to have resolved the issue. You should now be able to log in to the Facebook and Facebook Messenger apps from your Android device.
If you are still experiencing issues with the Facebook app, please make sure you have updated to the latest version of the app via the Google Play Store. We recommend keeping up to date with the latest updates where available.
Should you encounter any problems with in-app functionality please report the issue to Facebook via the 'Report a problem' option in the Facebook app settings. You can also check out Facebook's Help and Support.
We are investigating an issue where some customers are unable to log into the Facebook and Facebook Messenger apps on certain Android devices. While it doesn't appear unique to our customers it is proving challenging to isolate the specific cause and deploy a fix.