Canberra backrower Corey Harawira-Naera has been stretchered from the field during the club's match with South Sydney after collapsing during a break in play.
Harawira-Naera was waiting for a Rabbitohs drop-out during the 65th minute when he fell to the ground.
The New Zealand international appeared to have a seizure on the field as play was halted for close to 15 minutes.
"It was awful. I just spoke to the doctor and he said it was a seizure and they're unsure why. It doesn't seem to be any contact to the head, they're at a loss as to why it occurred," said Raiders coach Ricky Stuart.