The accident and emergency department at Ennis General Hospital was closed by the Mid-Western Health Board last night as an unofficial action taken by attendant staff worsened.
A board spokeswoman said the closure of the A & E department was a temporary measure to reduce the number of patients to manageable levels over the weekend.
She added that the situation was to be reviewed on Monday. In the meantime, emergency admissions are being dealt with at Limerick Regional Hospital.
Elective surgery, cleaning, delivery of essential patient supplies and removal of dirty linen and rubbish are no longer being carried out due to the action.
All 49 non-nursing staff are involved in the action which began on Wednesday.
The board spokeswoman said the situation was "very serious and in order to ensure patients safety, a range of options are being considered, including the transfer and discharge of patients".
According to the spokeswoman, essential services are being maintained through the co-operation of other staff at the hospital.
The action centres on attempts by attendants to change long-established work practices whereby attendants present menus to the ward sister or her deputy for signing.
Talks between SIPTU and the board aimed at ending the dispute failed to secure a resolution on Thursday.
The board spokeswoman said: "The care and safety of patients is our first priority and we are confident that given the co-operation of all concerned this will not be compromised.
"We take this opportunity to renew our appeal to the staff who have taken unofficial action to return to work."
Comment from SIPTU was unavailable last night.
