Latest: Wildlife experts say reports of a massive one-metre long rodent in the Royal Canal in Dublin are most likely a case of mistaken identity.
The semi-aquatic creature with orange teeth was originally thought to be an invasive rodent known as the Coypu.
Residents in West Dublin were warned not to approach the animal and to notify the authorities.
However, Waterways Ireland now believes the sighting is actually the native Irish otter.
They wrote on Facebook: "Earlier this week Waterways Ireland received notification of an unconfirmed report from the National Biodiversity Data Centre via National Parks and Wildlife Services of a Coypu on the Royal Canal.
"We are obliged to take this seriously, given the potential implications posed by a Coypu presence on Irish waterways.
"As there is a legal obligation to remove such invasive species from the wild, Waterways Ireland will continue to work closely with National Parks and Wildlife Service (NPWS) and the National Biodiversity Data Centre (NBDC).
"The public are encouraged to contact NBDC (www.biodiversityireland.ie) with any record of the invasive Coypu, preferably with a confirmation photo, if they happen to come across this species on any waterbody."
Earlier (12:37pm): Warning issued after large rodent spotted in Dublin
Waterways Ireland has issued an alert warning people in Dublin to be on the lookout for a large invasive rodent.
Sightings of the Coypu have been reported near the Ashtown area of the canal close to Castleknock.
This type of rodent - which has bright orange teeth and can grow up to one metre in length - weighs up to 9kg.
It can carry a number of diseases harmful to humans and domestic animals.
Ferdia Marnell from the National Parks & Wildlife Service is asking the public to report any sightings of the rodent:
"They're not aggressive, they're vegetarians, they only feed on aquatic vegetation really," he explained.
"But they are quite large and could be intimidating if they came across you unexpectedly."
Mr Marnell advised anyone who comes across the rodent to contact the National Parks & Wildlife Service.
"We are obliged under EU regulations to remove them from the wild," he added.