The Ministry of Prisons and Correctional Services has launched an inquiry following the escape from the new, multi-million dollar, high-security prison.
Corrections Minister Tialavea Tionisio Hunt told Parliament on Tuesday that there was breach of duty by a prison officer which led to the escape.
Talamua Online reports the officer, Usipani Simi, is alleged to have opened a door allowing the inmates to abscond.
He has reportedly been dismissed and charged.
Other prison officers who were on duty on Sunday morning are being investigated.
The minister said the inquiry would also examine why the two inmates, Lauititi Tualima and Aniseko Vaelei, who are notorious for escaping custody, were being held together in the same cell.