The Independent Police Conduct Authority has confirmed it was asked to investigate a senior constable who has admitted seeking sex for favours.
In the High Court in Christchurch on Monday, Gordon Meyer pleaded guilty to charges of corruption, bribery and sexual assault in relation to two women he sought sexual favours from in 2011.
On Tuesday, the IPCA said a matter relating to Meyer was referred to it by police in October 2007.
The investigation remains open and police believe it is highly possible that there are other cases involving Meyer, as sexual offending is generally under-reported. Police have set up a freephone number: 0800 22 33 70.