Bottas and his Mercedes had gone fastest in FP1 and did so again in FP2, but while on a long run made a move down the inside of Grojsean’s Haas towards the end of the second back straight.
The Finn bumped the Frenchman, turning his car around with both blaming each other, leading to them being summoned by the stewards for a meeting at 19:00 local time.
Grosjean was heard over his team radio saying: "What the f**k was that? Where did he come from?”
When asked if he had damage he replied: "Yeah, I think it's floor and everything.
"Mate, he was miles away. Check the car, if we can go again we go again, but I'm worried it's no good."
The session was red flagged as the debris from both cars was cleared, with Grosjean unable to return to the track while Bottas could.
But the Finn accepted responsibility for the crash to the stewards soon after, leading to his first reprimand of the season.
"Valtteri accepted responsibility for the collision and acknowledged that it was a failed attempt at an overtake, which resulted in the collision," the stewards stated (as quoted by Autosport).