.crc files in deep storage

Hi all,

We have found in our local deep storage files with the extension .crc:

$ ls -la data_source/2017-10-11T00:00:00.000Z_2017-10-11T01:00:00.000Z/2017-11-24T03:34:25.626Z/1/
total 155M
drwxr-xr-x 2 druid druid 4.0K Nov 24 07:43 .
drwxr-xr-x 4 druid druid 4.0K Nov 24 07:42 …
-rw-r–r-- 1 druid druid 1.8K Nov 24 07:43 descriptor.json
-rw-r–r-- 1 druid druid 24 Nov 24 07:43 .descriptor.json.crc
-rw-r–r-- 1 druid druid 154M Nov 24 07:43 index.zip
-rw-r–r-- 1 druid druid 1.2M Nov 24 07:43 .index.zip.crc

Does druid use these files? Can be safely deleted? Do you know which component generate these files?

Thanks in advance