The Coastguard says it has seen no sign of what was believed to be a three metre shark in the Whanganui River.
Police issued a warning at about 12.30pm on Saturday following reports of a dorsel fin around 200 metres north of the Dublin Street Bridge.
A Coastguard officer, Phil Palero, says dolphins and seals have been spotted in the river before so there is every possibility the shark sighting is accurate.
But he says whatever it is, it is likely to head back out to sea with the turning of the tide.
