Emergency services were called to the scene after the disturbance
Four people have been given fixed penalty notices after police were called to deal with "significant violence" at a gypsy site in Powys.
Dyfed-Powys Police said around 30 people were involved in Sunday's "serious public order incident" at Withy Beds Gypsy Site in Welshpool.
Of the 20 people arrested, 13 have been bailed for further police inquiries and three juveniles were released.
Fixed penalty notices require people to pay a fine of up to £80.
There was a large police presence at the site, including the force helicopter, on Sunday afternoon as travellers from Welshpool and Oxford were arrested for violent disorder.
A road diversion was also out in place around the camp and police stayed at the site overnight.
A recovery firm was also asked to collect four vehicles from the scene on Sunday.