UEFA, European football’s governing body, is preparing to bring criminal proceedings against FIFA President Gianni Infantino over an attempt to sell shares in the World Cup to private investors, according to reports from Sky Sports, the BBC, the Guardian and Al Jazeera.

The Guardian reported that the claims will be made in Switzerland and relate to alleged “criminal mismanagement” connected to Infantino’s failed FIFA Forward Enterprise plan. UEFA said it has applied for the release of documents related to the plan’s conception.

In what the Guardian described as an “explosive escalation of the war engulfing football’s governing bodies,” UEFA has made separate applications in the United States for information, including from FIFA. Al Jazeera reported that UEFA has asked a US court for FIFA documents to support the criminal case.

The BBC reported that UEFA is pursuing criminal proceedings against both FIFA and its president over the failed plan to sell off stakes in the World Cup. The plan itself has since been scrapped.

The underlying dispute centres on the proposal to sell shares in the World Cup, one of the sport’s most valuable assets, to private investors. UEFA’s move signals a significant deepening of tensions between the two governing bodies.

At the time of reporting, the sources did not detail any response from Infantino or FIFA to UEFA’s planned legal action, nor a timeline for when proceedings would formally begin.