Nearly all left-rear tyres at the end of Formula 1 first free practice showed damage from the kerbs around the Baku City Circuit, Pirelli has revealed.

The first time F1 has competed around the streets of the Azerbaijan capital city, though the circuit has drawn attention for its challenging layout, it was the kerbs that would prove the biggest teething issue for organisers after Pirelli reported cuts in the left-rear tyres after FP1.

Identified as being caused by the bolts in the kerbs not being drilled down far enough, modifications took place between the sessions and overnight to ensure there was to be no repeat. Indeed, though there were no tyre failures as a result of the oversight, Pirelli says nearly each left-rear was damaged.

"They investigated the kerbs after our information that we found, on most of the tyres used in the last part of FP1, some cuts on the left rear tyres," said Mario Isola. "I don't have the number but I can say 90% of the cars, so it was a good indication that something had to be investigated.

"All the cuts were in a certain position so they were more or less all the same and we informed immediately Charlie Whiting and he reacted immediately. He went out just before the GP2 qualifying session, checking all the kerbs on the left side of the car and he found a couple of them where the small bolts had come out. They fixed it, but they had to postpone the qualifying session for GP2, and I think they are going to also work on it tonight to have a final solution. In FP2, we checked the tyres used and we didn't find anything so everything is okay now.

With modifications to the circuit overnight including an extended pit-entry and the removal of some kerbs altogether, Isola admits the cuts were 'quite deep'.

"They were quite deep on the tread, touching the construction, but we didn't have any tyre failures or air loss, so it's something we have to fix but nothing happened.

"It's not my job to say if the drivers were lucky or not! Of course, we are here to make sure everything is running in the right way but as soon as any of our engineers give us information that they see something strange on the tyre, we go and check and we have a direct link to the FIA to be sure that we react quickly so that was exactly what happened."