A fourth little blue penguin in as many weeks had been affected by oil in north Otago's Oamaru Harbour.
- Little blue penguins continue Wellington City invasion
- Three little blue penguins stolen from their burrow with a crowbar in Hawke's Bay
The latest penguin was found coated in oil before the colony's staff took it into the rehabilitation centre on Wednesday, the Otago Daily Times reports.
According to the New Zealand Penguins website, the birds must be carefully cleaned if covered in oil, so they regain their natural oils before being released to the wild.
But mystery surrounds this particular find, with officials unable to determine where the oil is coming from, the ODT reports.
"This is really unusual to have this many come in at once," said Oamaru Blue Penguin Colony science and environmental manager Dr Phillipa Agnew.
"Four is not very many, but it is more than we would ever see in a year," Dr Agnew told the ODT.
NZ Penguins says washing the penguins is a slow process, requiring several washes with detergent.
"Once the feathers have been properly cleaned and the bird has been given a few days to waterproof its feathers using its natural oils, it can be released to the wild."