Redirect added, but not by me

Yesterday, I found a 301 redirect was set up to send /blog/post-name to /blog/amp_validated_url/b3v7420732f4eb87b3c8475. I did not create this redirect, but it was redirecting visitors to the home page instead of the blog post.

I deleted the redirect. Then, today, it is back. This time I disabled it.

How can I find out how this redirect is being created?

We recently installed the AMP plugin (the official AMP plugin for WordPress). I’m not sure if it’s related.