(CNN) -- Ferrari's Fernando Alonso was the fastest in Friday's second practice session at the Canadian Grand Prix as the controversy surrounding an alleged illegal tire test in Formula One rumbled on.
Alonso, third in the individual standings this season, posted a time of one minute 14.818 seconds to beat three-time race winner Lewis Hamilton of Mercedes by 0.012 seconds on the Gilles Villeneuve track in Montreal. Lotus' Romain Grosjean finished third.
Alonso was fourth in the day's opening practice session in wet conditions, three spots behind Paul di Resta of Force India.
"We can expect a very complicated weekend, because the weather is due to remain changeable right up to Sunday and judging the grip level will be difficult, both in qualifying and in the race," Alonso said.
But while the Spaniard was talking, Pirelli wasn't.
A day after Pirelli and Mercedes were summoned to the International Tribunal of Formula One's governing body to explain the alleged illegal test, Pirelli motorsport director Paul Hembery skipped a scheduled news conference in Montreal on the advice of the tire supplier's lawyers.
Red Bull and Ferrari lodged a protest last month, before the Monaco Grand Prix, over the tire testing done following the Spanish Grand Prix.
Although in-season testing isn't allowed, Pirelli has an agreement that says it can run 1,000 kilometers of testing with any marque during the season -- as long as every team is offered that opportunity.
When questioned by reporters at the news conference, Red Bull's team principal, Christian Horner, said the "lack of transparency" was "disappointing."
"I think it is important that there is transparency, of course," he said. "If a supplier has issues then it needs to obviously deal with them but when all entrants are supposedly equal, it's only right and proper that information is made transparently clear."
Mercedes team principal Ross Brawn said claims that it was a secret test were off the mark.
"I think anyone who believes you can go to Barcelona and do three days of testing, or 1000 kilometers of testing, and not have anyone become aware of it, is naive," Brawn said. "It was a private test, not a secret test, and sporting integrity is very, very important to us. Very important to Mercedes.
"And as I say I think when the facts become apparent then people can make a better judgment of the situation."
Meanwhile, championship leader Sebastian Vettel finished seventh in his Red Bull in the second practice session and predicted an open race Sunday.
"On one lap if you look at the timesheets, Mercedes was again very, very quick," he said. "And Ferrari looks competitive on both long and short runs, so I think those will be the main two rivals.
"Never forget the Lotus because they can be a surprise in the race by going further (on tires) than anyone else. So, for this race, it is difficult to say, but you need to keep an eye on all these teams I mentioned."
Mercedes' Nico Rosberg won the previous race in Monaco, where the pole sitter has a distinct advantage.
But in Montreal, where overtaking possibilities abound, only four times this century has the pole sitter gone on to win the race.