Ferrari was named for the first time in the federation statement late on Friday as having taken part in the tests carried out by F1's tyres supplier Pirelli.
World champion team Red Bull and Ferrari launched a protest at the recent 's Monaco GP because Mercedes did its tests with a 2013 car. The Ferrari tests were, it claimed, with a 2011 unit.
BOLD RED SHDS
"The federation has asked Mercedes and Ferrari, which have taken part in tyre tests in the 2013 season, to reply to a disciplinary inquiry in pursuance of IAF judicial and disciplinary rules," the statement said.
"This follows the sewards' report from the Monaco GP and represents supplementary information required by the IAF in the light of replies received from Pirelli, which was asked for clarification on Tuesday May 28."
News of the Mercedes tests cast a shadow over the their driver Nico Rosberg's in Monaco but Pirelli said it did nothing wrong; insisting that the tests were not secret and that Mercedes did not know what kind of rubber was used. Pirelli said the tyres were for the 2014 season and that it had invited other teams for tests.
Pirelli motorsport director Paul Hembery said: "Mercedes had no idea and still has no idea what was being tested. There was no benefit to it. The benefit was for Pirelli and F1 in general."
Red Bull believes Mercedes gained an unfair advantage while the Ferrari protest - the team wants a general in-season testing ban lifted - is to determine what is allowed and what not.
Pirelli has also come under fire through 2013 over quick tyre degradation which has led to many pit stops. All teams will be able to test a new tyre in free practice for Sunday's (May 9) 2013 Canadian GP but modified rubber will not be introduced until the following race in Britain.