An investigation is under way after an ambulance transporting a patient from Cork to Dublin for a lung transplant broke down.

It is believed the ambulance may have run out of diesel or may have had a problem with its fuel.

The patient had been on a waiting list for a transplant and got a call yesterday afternoon to report to the Mater Hospital in Dublin to undergo the operation.

A HSE ambulance operated by the National Ambulance Service was tasked to pick up the patient at his home outside Cork city and transfer him to Dublin.

Because of the urgency of the case, a garda escort accompanied the ambulance.

However, the ambulance broke down on the outskirts of Dublin, close to Newlands Cross.

The patient, who was mobile, is said to have walked from the ambulance to the garda car before being transferred to the Mater Hospital and undergoing the operation.

The National Ambulance Service said that it is investigating the incident.