Festive cheer and goodwill was in short supply in Newtown when people dressed as Santa were involved in a mass street brawl, say police.
The Santa race has taken place in Newtown since 2001
Officers used CS spray and batons to break up trouble amongst up to 30 people, following Newtown's annual charity Santa run.
There were five arrests hours after around 4,000 Santas finished racing.
Race organisers said if any official participants had been involved in the trouble, they would be banned in 2005.
Those arrested have all been released on police bail while further inquiries are carried out, Dyfed-Powys Police said on Thursday.
A number of others have been interviewed about their alleged involvement in the incident in the town's Severn Street on Sunday, which happened shortly after 2230 GMT.
Four officers suffered minor injuries during the scuffle and a total of eight were used to quell the disturbance, said police.
Pc Gareth Slaymaker, community safety officer for north Powys, confirmed that many of those involved in the alleged brawl were still wearing their Santa outfits.
"This is the sort of behaviour that gives a well-organised event a bad name, leading to the belief that it is just becoming a beer festival as mentioned in the press a few weeks ago," he said.
"Behaviour like this justifies the reluctance by the police to extend the licensing hours for public houses and bars for this type of event."
Dougie Bancroft, spokesman for the festive run's organisers Dial-a-Ride, said: "The trouble occurred seven hours after the Santa Run and I understand some people involved were dressed as Santa.
"But I'm not sure if they actually took part in the race because Santa suits were left by many in the town's park.
Thousands of Santas raised money for charity on Sunday
"If we find that people connected with the run, be it marshals, stewards or anyone else, were involved in the incident we will not tolerate them and they will not be involved in the race next year.
"We don't want anything to tarnish the reputation of the event or the charities which benefit from the Santa Run. We support the police in their action."
A Dyfed-Powys Police spokeswoman said: "A very successful Santa Run day at Newtown last Sunday was spoilt by the drunken behaviour of a number of local
individuals who managed to consume too much alcohol and became involved in a
serious public order incident."
"Police officers had to intervene an ongoing disturbance in Severn Street and more people then got involved.
"The police had to draw their batons and use CS
gas to quell the disturbance."
Montgomeryshire AM Mick Bates, who took part in the run, denied claims that it was turning into a beer festival.
"There's no way people can link the Santa run to the drunkenness and violence that ensued after the race," he said.
"I understand 200 charities will benefit from this year's run and the organisers do a wonderful job planning the event to make sure Newtown, Montgomeryshire, Dial-a-Ride and the charities get the most out of it.
"The problem with excessive drinking is not the responsibility of the Santa run but of pub landlords and individuals."
Last year, runners raised £80,000 for charities and it is hoped the 2004 total will be higher.
Organisers are still waiting to hear if they have broken the world record for having the most number of Santas in the same place.