Baku's inaugural grand prix is under a cloud due to a worrying problem with kerbs at the brand new street circuit.
GP2 qualifying was postponed on Friday, with Germany's Auto Motor und Sport reporting that 90% of the F1 cars in opening practice suffered damage to their tyres.
With the subsequent GP2 session red-flagged, Charlie Whiting and his delegation inspected the kerbs and found them loose and with sharp edges.
At the unprecedentedly-fast, wall-lined street track with small run-off zones, the risk of failing tyres is a major problem.
"I got my puncture on the lap [Daniel] Ricciardo crashed," said Sauber's Felipe Nasr.
"When I wanted to get back on track they told me the left rear tyre was damaged and we had no more."
Lewis Hamilton came top in the first practice session, followed by Nico Rosberg and Valtteri Bottas.
