A Wairarapa woman was arrested on suspicion of inciting racial disharmony after a hateful message was posted to her Facebook page in response to the Christchurch shootings.
The offence falls under the Human Rights Act and carries a maximum penalty of three months' imprisonment or a $7000 fine.
Police say a decision is still to be made about whether the woman will be charged and put before the court, or face an alternative resolution.
The Times-Age believes the woman is a parent to a child at a Masterton primary school, and parents complained to the principal and the police.
Senior Sergeant Jennifer Hansen said the Facebook post "upset a number of people because it referred to the events in Christchurch".