Photos of the victim of a serious assault which were splattered over a private Facebook page in Greymouth last week, are being investigated by the head of the West Coast police.

It follows an incident in Runanga on October 8 in which a group of three men and two women visited Shane Capstick at his Mills St residence and allegedly beat him.

Police did not initially report the beating to the media, but later confirmed it had taken place - after the victim had contacted the media.

Police confirmed the next day that they had arrested and charged three men and a woman with assault with intent to injure and assault with a weapon. A fifth person was being sought.

Capstick told the Greymouth Star that photos taken of him by police while he was at Grey Base Hospital on Saturday night awaiting treatment for his injuries had been posted on Facebook by serial social media poster Jacqui Galland under the pseudonym 'Jacqui Didit'.

After he contacted Galland "she emailed me police evidence photos" and told him they had come from a Greymouth policeman.

Capstick complained to the police the next morning.

On Friday, West Coast area commander Inspector Mel Aitken said she could not confirm if the photographs had come from the police or if they had been taken as evidence.

Aitken later confirmed that the two photographs in circulation on Facebook were taken by police and had been lawfully disclosed to the defendants in the case within the summary of facts when they appeared in court last week.

"Their actions of sharing and publishing this disclosure are now being investigated," she said.

Meanwhile, Aitken said the police did keep an eye on local Facebook and other social media pages as information posted may form part of "any intelligence gathering exercise" pursuant to an investigation.

"Those who choose to use social media to share messages should always be reminded to review their security settings if they want to be selective as to who can see what they have posted," she said.

"Further, users need to also be mindful that what they choose to post is in accordance with the terms of the site being used, as posts that may be offensive, threatening or unlawful in any way can and will be pursued by police."

- Greymouth Star