Kimi Raikkonen and Ferrari team-mate Sebastian Vettel dominated Friday's floodlit second free practice for this weekend's Bahrain Grand Prix. The Finn clocked a best lap time of one minute and 29.817 seconds around the Bahrain International Circuit to outpace four-time champion Vettel by 0.011 seconds. The two Ferrari men were comfortably clear by more than half a second of the two Mercedes of Valtteri Bottas and his team-mate and defending champion Briton Lewis Hamilton.
Raikkonen, however, faced a post-race investigation into a possible 'unsafe release' of his car, by Ferrari, following a routine pit-stop late in the session.
He pulled away, but then saw his pit crew waving their arms and pulled up at the side of the track.
If he is punished for an unsafe release because a wheel was not attached properly Raikkonen could face a grid position penalty.
Dutchman Max Verstappen, who missed the first session due to a power failure, was fifth for Red Bull ahead of team-mate Australian Daniel Ricciardo.
German Nico Hulkenberg was seventh for Renault ahead of the Toro Rosso of Frenchman Pierre Gasly and the two McLarens of two-time champion Fernando Alonso and Belgian Stoffel Vandoorne.
Earlier, despite his victory in the season-opening Australian Grand Prix, the four-time champion Vettel arrived in Bahrain on Thursday to play down hopes that it will be a straightforward task to win again on Sunday.
"If you look at the pace in testing and at the first race, it's pretty clear that Mercedes is fastest, probably with a three- or fourth-tenths' gap," he said.