The Yamaha rider ended the grand prix with his suit opened and without his chest protector, resulting in a three-second post-race time penalty dropping him to sixth, having already lost third to a three-second time penalty for a track limits violation.
Quartararo had no explanation for why his leathers came undone and said Alpinestars was looking into the issue.
He later said he should have been black-flagged and thus disqualified from the race for his suit problem as “it was not correct” behaviour in the wake of the Jason Dupasquier tragedy.
Current FIM rules on safety equipment states: “The equipment must be worn, correctly fastened, at all times during on-track activity.”
The manufacturer said on Tuesday that following a first assessment, they found “all zippers and fasteners fully functioning” and said all the suit’s componentry, including the Tech-Air Airbag System, was intact.
In a statement, Alpinestars said: “Following Sunday’s MotoGP race at the Circuit de Barcelona-Catalunya, the Alpinestars’ Racing Development team commenced an investigation into the integrity of Fabio Quartararo’s racing suit.
“Upon initial analysis post-race in the Alpinestars Racing Development truck located in the MotoGP paddock, the team found the suit to be in normal working order with all zippers and fasteners fully functioning.
Fabio Quartararo, Yamaha Factory Racing
Photo by: Gold and Goose / Motorsport Images
“Furthermore, all the suit’s componentry, including the Tech-Air® Airbag System, was intact and fully functioning. The Tech-Air® Airbag System did not deploy during the race, it functioned as expected, as there was not a crash situation.
“This is only a first assessment, to be further investigated once the suit is in the Alpinestars laboratory at Alpinestars headquarters, conducting all testing and analysis to understand more about the cause of what happened.”
After the incident, MotoGP world champion Joan Mir – who was fifth in the race – said he didn’t feel Quartararo should have been punished for completing the race with his leathers open, but felt the way he discarded his chest protector should cop a penalty.
“What I see as very dangerous is throwing the breastplate, it’s plastic and it’s dangerous, there are bikes coming at 200 km/h from behind,” Mir said.
“Of course, that is punishable, I think it puts the other riders in danger, that’s how it is.”
Johann Zarco, who was second at Barcelona, said he felt Quartararo’s actions would have warranted a black flag for disqualification “for his safety”.
Honda’s Marc Marquez believes it would be “unfair” to have disqualified Quartararo, but concedes he should have pulled out as a matter of safety.