Safe to delete appdata_* and updater-*?

Nextcloud version (eg, 10.0.2):
Operating system and version (eg, Ubuntu 16.04):
Apache or nginx version (eg, Apache 2.4.25): nginx/1.10.3 (Ubuntu)
PHP version (eg, 5.6): 7
Is this the first time you’ve seen this error?: Not applicable

Can you reliably replicate it? (If so, please outline steps): Not applicable

The issue you are facing: I have noticed some folders in the topmost level of my data directory taking up a considerable amount of space (multiple gb). Judging by the naming scheme they seem like ad-hoc backups (appdata_ocjx58mjh67j and updater-ocjx58mjh67j). Is it safe to remove those folders? How did they end up there in the first place, is there an explanation for this? An aborted update maybe?

Thanks in advance!