An interim review into the Pseudomonas outbreak in which babies died in hospitals in Derry and Belfast is critical of a lack of communication between health officials.
The Regulation and Quality Improvement Authority (RQIA) is investigating the four deaths which took place in December and January.
The review team found there was no common approach across neonatal units for declaring an outbreak.
Its report has concluded that the bug was linked to water from contaminated taps in neonatal units.
The independent review team, led by Professor Pat Troop, also found there was a lack of communication between staff in health trusts during the outbreak.
They said this lack of structure and co-ordination may have impacted on how decisions were made.
One baby died at Altnagelvin Hospital in December while three babies died in Belfast’s Royal Jubilee Maternity Unit in January.
The RQIA interim report was presented to the Assembly health committee at Stormont yesterday.
The team said it believed the most likely method of spread to babies was the use of tap water in washing during nappy changes.
It has recommended that, in future, only sterile water is used for washing babies in neonatal units.
Its first stage addresses the causes and impact of the outbreak and the full report is due by the end of May.