The McLaren team has been summoned by the British Grand Prix stewards after fitting one of Jenson Button's tyres on Fernando Alonso's car during qualifying.
McLaren boss Eric Boullier confirmed the mistake, which will likely mean the Spanish driver will be disqualified from qualifying.
Boullier said the mistake was caused by confusion during a double pitstop during Q1.
Alonso had qualified in 17th position after another difficult day for the team and looks now set to start from the back of the grid.
Representatives from the team were summoned to see the stewards.
Teammate Jenson Button was 18th, only ahead of the Manors.