The devastated mother of a newborn boy who died when he was mistakenly given the wrong gas at a Sydney hospital has described how she held her baby's lifeless body and urged him to "Wake up, wake up".

"I held my baby, they [brought] him to me at the hospital," the mother, Sonya Ghanem, told Channel Nine.

"I said 'I want to see him'. Just looking at him, shaking. 'My son, wake up', I would tell him. 'Wake up, wake up. What did they do to you?'"

The baby boy, named John, died at Bankstown-Lidcombe Hospital on July 13 after NSW Health Minister Jillian Skinner said he was mistakenly treated with nitrous oxide, commonly known as "happy gas", instead of oxygen in the the hospital's neonatal resuscitation unit.

Another baby boy, born in June, remains in a critical condition after he also was mistakenly treated with nitrous oxide. Channel Nine reported that that baby boy has suffered brain damage.

Ms Skinner said the oxygen outlet in one of the hospital's theatres was incorrectly installed with nitrous oxide, rather than oxygen, and certified by BOC Limited in July 2015.

The error was discovered last Thursday after a paediatrician raised concerns about the unexpected death of the second baby.

"I am profoundly sorry for the families of a newborn who died and another newborn who was severely affected," Ms Skinner said in a statement.

"I deeply regret these families have suffered through such a devastating error. NSW Health will do all it can to support them."

Nine reported that NSW Health officials told Ms Ghanem and her husband, Youssef, of the fatal error on Saturday morning, 10 days after their baby's death.

Ms Ghanem said she had gone to Bankstown-Lidcombe Hospital on July 13 and was in labour for several hours before doctors told her she needed to undergo an emergency caesarean.

She told Channel Nine she was put under general anaesthetic. Ms Ghanem said when she woke up, she was told by a nurse that her baby son had died.

The baby's death has been referred to the coroner.

All eight operating theatres at Bankstown-Lidcombe Hospital have now been checked and no other outlets were found to be faulty, Ms Skinner said. The outlet responsible has been fixed, but the theatre remains closed, Ms Skinner said in a statement.

Bankstown-Lidcombe Hospital has reviewed all records of babies delivered in this theatre since July 2015 and confirmed no other baby received gas from the affected outlet.

Ms Skinner said the Government had contacted BOC Limited "demanding urgent advice" on how the incorrect installation had occurred.

In a statement, BOC expressed "profound sorrow" for the families affected by the "devastating tragedy".

"We deeply regret that these families are suffering pain and sorrow," the statement said.

"As soon as BOC was notified of the situation we cooperated fully with all investigations being undertaken by the NSW Government - the Hospital, the NSW Coroner, and the Ministry of Health teams.

"It is extremely important to identify the exact cause of this tragedy.

"BOC is also conducting a full internal enquiry and has appointed a special investigation team to ensure that the cause is clearly identified.

"BOC will work closely with the Ministry of Health throughout these investigations."

The Opposition's health spokesman Walt Secord said Ms Skinner must launch an independent review.

smh.com.au