I am using Moodle 2.3.1+. In /moodledata/temp folder, found a number of huge files with file name convention "assignment_XXXXXX", which is similar to the following. These files occupied large disk space.

rw-rw-rw 1 apache apache 3299286695 Nov 25 21:49 assignment_99ANpD
rw-rw-rw 1 apache apache 7227990780 Jan 8 01:15 assignment_dFNgsQ
rw-rw-rw 1 apache apache 3299286695 Nov 29 23:45 assignment_E7hYiP
rw-rw-rw 1 apache apache 2934456331 Dec 4 10:01 assignment_GermEm
rw-rw-rw 1 apache apache 3133176562 Jan 8 09:03 assignment_hNg6hA
rw-rw-rw 1 apache apache 7612406653 Jan 20 17:39 assignment_IAaX6U
rw-rw-rw 1 apache apache 3299286695 Nov 25 21:45 assignment_T0FatG
rw-rw-rw 1 apache apache 6258691590 Jan 8 08:55 assignment_VIMftT
rw-rw-rw 1 apache apache 6258691590 Jan 8 08:35 assignment_VWOJ5t
rw-rw-rw 1 apache apache 2934456331 Dec 4 09:51 assignment_wlyGK5

I want check with you what are these files, and why the files are created in /temp folder? Is it safe to remove these files directly from server?