Formula One's governing body said it had opened an investigation into Romain Grosjean's Bahrain Grand Prix crash on Thursday as the French driver hailed those who helped him escape the fireball.
Grosjean suffered burns to his hands after his Haas car split in two, penetrating a metal barrier and erupting in flames, in Sunday's race.
The Frenchman left hospital on Wednesday and in an Instagram post accompanying video footage pointed to "the moment I realized I was going to live'.
He highlighted the 'professionalism' of the marshal with the extinguisher and FIA doctor Ian Roberts.
"I told him he was a hero, he went into the fire as much as he could to save me," he said of Roberts.