Racing Bulls driver Liam Lawson said he "could have killed" marshals who ran across the track in front of him at the Mexican Grand Prix.
Marshals were deployed to collect debris on track as Lawson was released from the pits.
Videos show two running across the circuit just in front of the New Zealander.
"Oh my God, are you kidding me? Did you just see that?" Lawson said on the radio.
"I could have f*****g killed them mate!"
He added after the race: "I honestly couldn't believe what I was seeing. I got to turn one and there were just two dudes running across the track.
"I nearly hit one of them, honestly, it was so dangerous. I’ve never experienced that before and I haven’t really seen that in the past. It’s pretty unacceptable.
"We can’t understand how on a live track, marshals can be allowed to just run across the track like that. I have no idea why, I’m sure we’ll get some sort of explanation, but it really can’t happen again."
Marshals fall under the responsibility of the FIA and the race director.
An FIA statement read: "Following a turn one incident, Race Control was informed that debris was present on the track at the apex of that corner.
"On lap 3, marshals were alerted and placed on standby to enter the track and recover the debris once all cars had passed turn one. As soon as it became apparent that Lawson had pitted, the instructions to dispatch marshals were rescinded, and a double yellow flag was shown in that area.
"We are still investigating what occurred after that point."
