Reports of an oil spill in Lyttelton Harbour this week have been discounted after investigations found the "slick" was in fact an algal bloom.
Environment Canterbury says tests showed the discoloured water was a non-toxic algal bloom which looked like oil from a distance.
"Once you get closer you can see that the coloured particles are under the surface of the water, rather on the top where oil would float," ECan's Jim Dilley said.
NZN