Poland’s financial industry regulator on Friday informed the prosecutor’s office about a possible case of market manipulation involving a person acting in the name of JPMorgan Securities.

The complaint stems from the unusual end to trading on the Warsaw stock exchange on November 12. The market’s blue-chip WIG20 index had slumped by 9.1 per cent during the day, but minutes before the session’s close a series of buy orders worth 130m zlotys ($42m, €34m, £28m) were executed on all the companies making up the index, driving the WIG20 sharply upwards.