The two clubs played each other at the CBS Arena
Police said they were searching for people who put up an offensive banner aimed at Leicester City fans ahead of their Midlands derby with Coventry.
Warwickshire Police said it referenced the helicopter crash which killed the club's chairman and was hung over the A444 in Exhall on Saturday.
Insp Mark Calvert said the sign, one of several seized in the region, "looked like it had been professionally made".
Both football clubs condemned those who put offensive banners up.
The Sky Blues said at the weekend they were working with West Midlands Police to "identify those who created and displayed" such banners over the M69 ahead of the match on Saturday.