strange files in wordpress wp-admin folder

Hello
I am seeing a series of large files in the wordpress wp-admin directory of a site I’m working on. I have not seen these files before on other sites so I’m not sure what they are. There are quite a few of them and they range in size from 40-150MB. The file names are all similar:
core.2180
core.2575
etc
They are all names core.####. I security scan of the site found no threats detected.
Anyone know what these files might be?
Thanks