A woman is fighting for her life after the tent she was sleeping in was allegedly run over by a vehicle.
Three other campers were also injured at the Rhyd y Galen campsite near Caernarfon in north Wales.
Paramedics, firefighters and police officers were called to the scene at around 2am today after the incident.
Two men have been arrested, North Wales Police said in a statement.
DCI Sion Williams said: “This was a terrifying event for people who should have felt safe in their tents.
“North Wales Police are supporting those involved and our thoughts are with the family of the woman who has been seriously injured.
“I would like to thank those members of the public who have helped us, but if anyone has not been spoken to yet and has any information which could assist, then please contact us.
“Our Roads Policing Unit is working with detectives to establish exactly what happened.”
It is not known at this stage what the men have been arrested on suspicion of.
A Welsh Ambulance Service spokesman said: “We were called at approximately 2.02am to reports of a collision between a vehicle and a tent in Caernarfon.
“We responded with two emergency ambulances.
“One patient was transported to Ysbyty Gwynedd Hospital, Bangor.”