The Health Service Executive has said there was no patient on board an ambulance that lost a wheel in the early hours of yesterday morning.
However, a source in the National Ambulance Service (NAS) said: "This vehicle had just been used to bring a sick person to hospital in Drogheda and was returning to Dundalk at 5am when the wheel came off it.
"It was only going at 20km/h when the crew felt the jolt."
The NAS said the vehicle will be subject to a technical examination to see what happened.
It said: "The ambulance crew were uninjured and resumed duty in another vehicle."