An ambulance crew in Cork was suspended for refusing to transport a patient to Dublin, a union has confirmed.
It is understood that the patient was a sick child and was later brought to Crumlin Children's Hospital by another crew.
A spokesperson for the National Ambulance Service Representative Association - a branch of the Psychiatric Nurses Association - confirmed that the crew was asked to make a run to Dublin at the end of a 12-hour shift on Thursday morning.
He said they made an assessment on health and safety grounds that it would be unsafe to make the journey after working long hours.
The spokesperson confirmed that members of the crew that were suspended were Nasra members.
However, he said the crew were acting on their own account and not as members of any union.
Sources said other crew members refused to work in support of their suspended colleagues following the incident. They said they gave the HSE an ultimatum to reinstate the crew members.
In a statement, the HSE said it is satisfied that there was no impact "regarding continuity of service".
"The National Ambulance Service is currently investigating an issue that occurred locally and would therefore not be in a position to comment any further at this time," it said.
Some 500 of the Psychiatric Nurses Association's paramedic members are due to go on strike next Tuesday.
The row is over their demand that the HSE recognises the union as its representative organisation.
It accused the HSE of refusing to respond to invitations from the Workplace Relations Commissions to talks to resolve the dispute.
General Secretary Peter Hughes claimed the HSE has ignored two requests from the WRC to attend talks.
"For the HSE to refuse to attend Workplace Relations Commission talks and continue to attempt to resolve this dispute through their lawyers is irresponsible in the extreme, and goes against all standards of good industrial relations," he said.
"Highly professional and dedicated ambulance personnel find themselves forced to the brink of a national strike because of an incomprehensible stand by the HSE to try to deny them the right to be members of the union of their choice, and to force them to be members of a union that they have repeatedly shown they do not want to be members of."
He said he has written to Health Minister Simon Harris, to alert him to the HSE's refusal to attend talks. This includes discussions on strike contingency plans.