He has since been released on bail pending further investigation.
Slot will become the first manager from the Netherlands to take charge of Liverpool when he resumes his new role in June.
The match was first halted after seven minutes when smoke bombs were thrown onto the pitch from a stand with Groningen fans.
Manchester United has been drawn to face La Liga side Real Betis in a two-legged UEFA Europa League round of 16 fixture.
UEFA announced that the finances of Man City, Barcelona, Chelsea and the other 15 clubs will be monitored closely for the remainder of the year.
Tammy Abraham scored the only goal as Roma defeated Leicester City 1-0 on Thursday in Rome to reach the inaugural Europa Conference League final.
