Durham Police were called just after 7.30pm last night (October 13) and said four boys, aged 17, 15 and 14 were arrested on suspicion of grievous bodily harm with intent.
One person suffered a head injury and was taken to hospital.
Police at North Park, Darlington last night(Image: Terry Blackburn)
A full force statement reads: "Police were called just after 7.30pm last night (October 13) to reports of an assault in North Park, Darlington.
"The victim was taken to Darlington memorial hospital with a head injury.
Crime scene investigators were seen in the park late last night(Image: UGC)
"Four boys, aged 17, 15 and 14 were arrested on suspicion of assault GBH with intent.
"They remain in custody while further enquiries are carried out."
Pictures taken last night show a police van stationed at the scene while crime scene investigators, carrying torches, take evidence pictures.
The North East Ambulance Service (NEAS) said they also attended the incident but were called to a private address.
A spokesperson confirmed: "We were called to an incident at a private address in Darlington last night (13 October) shortly before 7.30pm.
"We dispatched one ambulance crew and one patient was taken to hospital."