Formula One supremo Bernie Ecclestone says the circumstances of Fernando Alonso's testing crash are "completely inexplicable".
"What has surprised me is what happened (at Barcelona). It is completely inexplicable, for him as well," Ecclestone is quoted as saying the by DPA news agency.
"Fernando is a little surprised by what has happened to him."
Amid speculation about the cause of the crash and Alonso's medical condition, the 84-year-old Briton said the FIA is now looking into it.
"McLaren doesn't want to discuss it, so there's not much we can do," said Ecclestone.
"It is really a sporting issue. So maybe it is one of those things that is necessary for the FIA to investigate."
Former F1 doctor Gary Hartstein said the mystery would grow deeper if Alonso also sits out Malaysia.
"That would be head-scratching time, for sure," he told the BBC.
"It would be highly unusual - so much so that they'd have to say something. But for now concussion is the most likely and it explains everything we know at the moment."