The Football Association is investigating a banner unfurled by Crystal Palace fans that depicted Nottingham Forest owner Evangelos Marinakis holding a gun to midfielder Morgan Gibbs-White's head.

Forest are hugely disappointed that supporters were permitted to bring the banner into Selhurst Park, according to well-placed sources.

Crystal Palace have been approached for comment by the BBC.

Palace and Forest played out a 1-1 draw at Selhurst Park on Sunday, but the clash was overshadowed by the banner which, in addition to the portrayal of Marinakis pointing a gun towards Gibbs-White, read: "Mr Marinakis is not involved in blackmail, match-fixing, drug trafficking or corruption!"

Marinakis has consistently denied any wrongdoing in relation to such allegations.

The FA is probing the banner and will decide whether Palace face punishment.

There are strict rules regarding messaging contained in such banners regarding foul language and defamatory, political and offensive slogans.

The banner will serve to heighten tensions between the two clubs following a controversial summer that saw Palace relegated into the Europa Conference League with Forest taking their place in the Europa League after the London club contravened Uefa's multi-club ownership rules.

Last month, Palace chairman Steve Parish said the decision to remove Crystal Palace from the Europa League was "the biggest injustice in the history of football".

However, there is now major frustration at the City Ground that more was not done to prevent the banner from being displayed.

The banner is viewed at Forest as being inflammatory and xenophobic. They are privately questioning why Palace and the club's ownership group consisting of Woody Johnson, Parish, Josh Harris and David Blitzer have not publicly criticised the banner.

Gibbs-White came close to leaving Forest for Tottenham earlier this summer after the London club appeared to trigger the England international's £60m release clause.

But the midfielder ended up staying at the City Ground, signing a new deal,, external and speaking about his decision to stay in an interview alongside Marinakis.