The Independent Police Conduct Authority has received a complaint over a raid involving police and immigration officers.
The case - which relates to an incident in October - concerns an overstayer in Te Puke, Pooja Kapila, who is being deported, along with her family.
The complaint alleges police prised open her fist and forced her thumb onto a piece of paper to get a print for a travel document.
It came from the woman's immigration adviser, former cabinet minister Tuariki Delamere and was witnessed by a Maori Anglican minister, Marilynn Williams.
She said two police officers had been involved in the incident.
Mr Delamere says his complaint is based on Ms Williams testimony and he told Checkpoint police and immigration officials have no powers under New Zealand laws to use pain and force to get someone to sign a document.
The Conduct Authority has referred the case back to police for further investigation before deciding whether to conduct an inquiry of its own.
Bay of Plenty police say they they were working with immigration officials and were asked to obtain fingerprints.
They say they are taking the complaint seriously.