Corrections officials are investigating claims of sexual favours at a women's prison in south Auckland.

In one case, it's claimed a female guard was given a nude full body massage by an inmate.

A male guard is also being investigated, over claims he brought in contraband in exchange for sex.

The allegations were made by a former inmate at Auckland Regional Women's Correctional Facility.

The woman, whom the Herald on Sunday agreed not to name, said a prison boss tried to tell her the massage did not happen. "[But] I saw it. It was full body and nude. It was in a cell with the door open."

The former inmate, who was released in October after serving a four-and-a-half-month sentence, said another officer told her a male colleague had given an inmate contraband in exchange for sexual favours. She later saw the inmate with food not available behind bars.

Department of Corrections corporate services deputy chief executive Vincent Arbuckle confirmed the woman had made a number of complaints and they were being treated seriously.

Arbuckle would not comment further on the investigation or what had already been established. He did not known when the investigation would be completed.