Lewis Hamilton's pole position is hanging in the balance after the McLaren driver stopped on track having taken pole.
Although McLaren are refusing to disclose the reason why Hamilton stopped, the Brit will have to do so in a stewards' meeting.
Under the F1 regulations, all drivers have to return to parc ferme after qualifying with a minimum of one litre of fuel in their tanks.
If a driver fails to do just that, they have to appear before the stewards and explain the reasoning.
As such, Hamilton is at present in with the stewards, although his team boss Martin Whitmarsh is adamant the Brit's MP4-27 had enough fuel to reach parc ferme and comply with the one-litre rule.
"There was enough fuel to take a fuel sample, but we stopped the car - and we are now talking to the stewards about that. There was 1.3-litres of fuel taken out of the car," Whitmarsh told Autosport.
Asked if he was confident that Hamilton would retain his pole position, the team boss said: "I don't know. But I hope so.
"Lewis did a fantastic job throughout that session and we have all seen how difficult it is at the moment to be consistent, to switch everything on at the right time.
"Lewis and his team did a great job, so it was a massive margin by the situation within F1 at the moment so undoubtedly he deserves to be there."
Earlier Whitmarsh had revealed that the issue was neither a gearbox nor an engine problem. That, though, was before the stewards investigation.
Whitmarsh downplays Hamilton concerns