BRUSSELS (AP) — The European Union's competition watchdog is stepping up its investigation of a U.S. video game platform and five game makers over concerns they blocked players from buying cheaper versions of games in other countries.

The EU's competition commissioner said Friday it issued a statement of objections to Valve Corp., which owns the Steam online PC game distribution platform, and the computer game publishers Bandai Namco, Capcom, Focus Home, KochMedia and ZeniMax.

The commission, which started looking into the issue two years ago, said the companies breached the bloc's antitrust rules by agreeing to use "geo-blocked activation keys" to prevent cross-border game sales.

Competition Commissioner Margrethe Vestager said the companies prevented game players from shopping around for the best price and they now have a chance to respond to her concerns.