A 50-tonne crane is on its side on a barge in Milford Sound. Clean-up crews are ready in case any oil leaks into the water.
Some 1600 litres of hydraulic oil and 200 litres of diesel are sealed in the crane.
Southland Regional Council describes the scene as stable.
The Department of Labour and Maritime New Zealand are investigating the incident, which happened at about 2pm on Wednesday.