Red Bull has rejected suggestions world champion Max Verstappen and Sergio Perez simply ran out of fuel last Sunday in the 2022 season opener.
The duo was on its way to 2nd and 4th places in the closing stages of the Bahrain race until Verstappen began to complain of steering and battery problems.
But Red Bull said it was a fuel system problem that caused the DNF on both cars.
"The battery had nothing to do with it," Dr Helmut Marko told ORF.
"That's what Max thought, but we don't have a final explanation. It's all just speculation for now."
Some publications quoted both Marko and Verstappen as saying the problem was that the engine 'had no fuel', triggering speculation it was a simply team miscalculation.
The Dutch newspaper De Telegraaf cited sources in ruling out a fuel pump failure, with Marko insisting that it's a standard part that "doesn't come from our factory".
Marko also denied that Red Bull was caught out with its fuel calculations.
"We did tests in which we emptied the tanks down to one litre," he insisted. "We have no conclusive explanation."
A team spokesman, meanwhile, said a "full, comprehensive investigation" is currently underway.
"We will refrain from further comment," the spokesman said.
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