Zurich, Switzerland -- (Sports Network) - The International Ice Hockey Federation informed the NHL, NHL's Players' Association and Russia's new Continental Hockey League (KHL) that the contracts of six players are being investigated.

Alexander Radulov, Nikita Filatov, Thomas Mojzis, Jason Krog, Fedor Fedorov and Viktor Tikhonov are all involved in transfers to, or from, Russia and must submit documentation to the IIHF for review by July 31.

Until the investigations are finalized, all concerned parties will be suspended from international transfers and competitions.

"We hope that this can be resolved amicably and in a timely manner," said IIHF president Rene Fasel. "It is unfortunate that we are already facing such difficulties after the progress that was made last week. I am hoping that all sides can come to a solution."

The investigation comes just one week after the IIHF, NHL and its Players' Association agreed to respect contracts and not sign players who are under contractual obligation.