A 5.5 earthquake has rattled Milford Sound early this morning and has been largely felt in the Queenstown and Wanaka areas.
The quake, centred north-east of Milford Sound, occured at 3.24am and was 5km deep.
Over 600 people reported feeling the earthquake.
The siesmologist on duty has confirmed the quake looks to have occured on the Alpine Fault, GeoNet said in a Tweet.
"This fault system has the potential for larger events and we would like to make sure that you are prepared for a large earthquake at all times," GeoNet tweeted.