Investigations are continuing following a collision outside the Calder Gate entrance to Sellafield this morning.
Reports suggest the overall incident involved two vehicles – an Isuzu D-Max and a Polaris Ranger.
The Polaris Ranger was reportedly in collision with two pedestrians. Police received a report at 8.55am.
One of the pedestrians, a man aged 55, was taken to the West Cumberland Hospital with serious injuries. He remains in a serious condition.
The other, a man aged 39, also attended hospital. His injuries are not serious at this time.
Four people – all from the local area - have now been arrested in connection with the incident.
They are: four males, aged 16, 19, 50 and 52. They are in custody on suspicion of dangerous driving and causing grievous bodily harm with intent.
Officers are aware the incident has caused concern in the community and are liaising with the organisers of the industrial action at this location to offer reassurance.
There is no wider threat to the public.
Extensive investigations are continuing and police would ask people do not share any footage circulating online or speculate about the circumstances. We are aware of inaccurate speculation online.
Anyone with information about the incident can contact police on 101, referring to incident 33 of September 17.