Police are looking for five people who were caught on CCTV cameras vandalising the Homer Tunnel on State Highway 94 between Te Anau and Milford Sound.
Police in Te Anau said four men and a woman walked the length of the 1.2 km tunnel late at night a week ago using what appears to have been a spade handle to smash most of the 36 lights.
The tunnel has been closed at times for repairs costing $10,000.
Police in Te Anau would like to hear from anyone who has any information.
