Sebastian Vettel says Ferrari is still investigating the cause of his stoppage during practice for the Bahrain Grand Prix, as he missed out on track time.
Vettel lost power exiting Turn 4 and later appeared to be inspecting a loose wheel on the left rear of his SF16-H, after pulling over with 15 minutes remaining in the second session.
Vettel, who finished the day in sixth position, says that Ferrari adopted a cautious approach in order to avoid potential damage to the car.
"We don't know 100% what happened," he said. "I felt out of Turn 4 that I lost drive, so I decided to stop.
"Obviously we don't want to take a risk at this stage, damaging the car or the engine. It's a shame because I would have loved to cover more laps, but that's what it is.
"Obviously, it was incredibly important to do the mileage today and get the information on Friday, but it's even more important to make sure that the car is in good conditions for the whole weekend and for the whole season."