Police said samples from the post mortem for the two infants had also been sent overseas for further medical analysis.
Meanwhile, the Samoa Medical Association has expressed grave concern over the deaths.
The Association's President, Dr Tanyamarie Petaia said, in a statement, the medical association believes that as health care providers in Samoa they have an astronomical task ahead in regaining people's confidence in the safety of the health service.
In particular, she said the continuation of the expanded programme of immunisation in the future was an issue of concern.
The president also said the Medical Association unites with all Samoa health care professionals and providers in expressing their sincere apologies for inadvertently causing pain and sadness to the families of the two deceased infants.