UEFA is withholding Europa League champion Atletico Madrid's prize money from this season's competition while it investigates the club for breaching "financial fair play" rules.
UEFA says Atletico is among 23 clubs whose prize money from this season's Champions League or Europa League could be stopped because of overdue payments of transfer fees, wages and social taxes up to the end of June.
Malaga, Sporting Lisbon and Fenerbahce also are being investigated.
The list of offending clubs was drawn up by Jean-Luc Dehaene, the former prime minister of Belgium who heads the panel appointed by UEFA to prosecute financial fair play cases.
UEFA says the clubs have until Sept. 30 "to provide an updated situation."
