Gardai are investigating a suspected hoax 999 call, which sparked a major emergency response on the River Shannon earlier tonight.
According to sources, a call was made around 8pm to the emergency services that a person had jumped into the river from the "Railway Bridge", at Long Pavement, Limerick.
It is understood two youths ran up to a man who was out walking his dog along the river bank and told him they had seen someone jump into the river.
The man is said to have phoned 999 in good faith, and delivered the details of the alert.
In all, approximately 36 emergency service personnel responded to the alert.
The Coast Guard rescue helicopter 115, was dispatched from its base in Shannon and combed the river for over an hour.
A 16-man crew attached to Limerick Marine Search and Rescue Service (LMSRS) responded to the scene, including two five-man teams on water crafts as well as a crew of six on board a swift-water rescue truck.
A spokesman for LMSR said: "As far as we know it was a hoax call."
"Two lads came up to a man out walking his dog and said they saw a person jumping off a bridge. The man rang it in," they added.
"We stood down the operation around 10 past nine," they said.
Twelve firemen, including a number of their members specifically trained in river rescues, responded to the scene.
Gardai and the ambulance service also responded.
Meanwhile, another source added: "Limerick City Fire and Rescue Service sent three fire tenders and their rescue boat to the scene.
"The fire service were joined by the Limerick Marine Search and Rescue Service and the Shannon-based rescue 115 helicopter."
"An extensive search was carried out and at the moment nothing has been found."
"The Gardai are investigating," the source added.