Hi,
I recommend you do some investigation to gather more information about how/when the snapshots were created.
In the Azure portal, please navigate to your subscription -- Activity log blade. Click Timespan and select Last month. In the search box just above the items, enter snap
For each item, click the arrow on the left to expand it, then click on items to examine details. For example, you can see the user account that initiated create snapshot of a disk. Take a careful look at the information on JSON tab for important information such as IP address (ipaddr), appid, etc.
What user created/updated the snapshots? Did the request come from your IP address, or some other unknown address? What appid made the request?
Thanks.
-TP