A union representing most prison guards is trying to find out why its office was searched last week, by people it believes were Corrections Department staff.
The Corrections Association says documents were seized during the raid in Hastings.
In a memo leaked to Radio New Zealand, the association says it has launched legal action to discover why the documents were removed.
It says the people who searched the office were the department's professional standards staff and the police.
The Corrections Department has declined to comment.
Fraud complaint being prepared
Meanwhile, in an unrelated matter, a former executive member of the association is preparing to lay a police complaint about credit card misuse in its ranks.
Helen Williams, who recently stepped down as the union's northern region representative, says members of the national executive wouldn't say why a helicopter ride, housepaint and an emergency passport were among the items paid for by a union credit card in recent years.
The association, which has about 2800 members, recently lifted its fortnightly fee to $17.50.