Mercedes were at the centre of uproar over the Monaco Grand Prix weekend after it emerged they used their 2013 car to assist Pirelli in a 1,000km test of next year's tyres in Barcelona in mid-May.
Ferrari, along with Red Bull, protested against Mercedes' actions prior to Sunday's race around the Principality, although it has since emerged the Italian team also took part in a Pirelli test between the grands prix in Bahrain and Spain.
Ferrari used their 2011 car, in apparent compliance with the regulations, and had their customer car division, Corse Clienti, conduct the test, rather than their own race team.
However, Ferrari still appear to have questions to answer.
"The FIA has asked Team Mercedes AMG Petronas F1 and Scuderia Ferrari Team, which have taken part in tyre tests in the 2013 season, to reply to a disciplinary inquiry in pursuance of the FIA Judicial and Disciplinary Rules," an FIA statement read.
"This follows the stewards' report from the Monaco Grand Prix and represents supplementary information required by the FIA in the light of the replies received from Pirelli, who were asked for clarifications on Tuesday May 28."
Pirelli today defended itself in the row over the Mercedes test, saying it was the company's understanding that the German team had cleared the test after "good discussion" with the FIA.
On Sunday, Mercedes team principal Ross Brawn stated: "It was up to Pirelli to spread the information. It wasn't up to us, it was their test."
Today, however, Pirelli motorsport director Paul Hembery laid the blame squarely on Mercedes.
"For these tests, as with others, we requested the use of a representative car," Hembery said.
"We wanted to create a test that gave us great value. It has been suggested in some quarters we asked for a 2013 car, that's not true.
"We asked for a representative car. Our understanding is there was good discussion between Mercedes and the FIA on this subject."
Hembery added that Mercedes gained no advantage from the Barcelona test, as the tyres being examined were for use in next year's championship, and claimed the test was not secret in any way.
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