A two-year-old girl died from complications associated with drug poisoning, but it's not clear what drugs she took or how she got her hands on them.
Several babies, the oldest only six months old, died from undetermined causes linked to unsafe sleeping or bed sharing.
In each case, it's not clear what, if anything, could have been done differently to save these children, who were all known to the Department of Social Development.
The causes of the children's deaths, which date back to 2010, have remained secret for years, protected as private health information.
CBC News has obtained new details on these cases from the chief coroner through access to information.
It comes as the provincial government has promised to tell the public more information about how vulnerable children are dying, including each child's age and cause of death.
But the revamped reporting process, introduced last December, does not reveal when the system fails a child.
Nor does it provide the full narrative of what happened to the child, something provinces like British Columbia and Alberta provide to the public.
'Far less than transparent'
It's not good enough for Bernard Richard, a former child and youth advocate in both New Brunswick and British Columbia.
"It's far less than transparent," said Richard, now a senior adviser with Mi'kmaq NB Child and Family Services Inc.
The province's child death review committee is mandated to review the deaths of children under the age of 19, including children who have been in contact with the Department of Social Development within a year of the child's death.
CBC News was provided new details on 51 cases dating back to 2010.
All of the recommendations stemming from each case have been previously reported. But until now, the public didn't know the children's ages or causes of death.
A little more than half of the children died from natural causes, ranging from cancer to rare genetic disorders.
Four teenagers, ranging in age from 15 to 18, died by suicide.
Four more children died from motor vehicle collisions or "upsets" or recreational vehicle accidents. The youngest was only 20 months old.
Another died from a motor vehicle-pedestrian collision, and two more died from drowning after a motor vehicle crash.
One teenager — 18-year-old Baylee Wylie — died by homicide in a "violent altercation." The documents don't provide Wylie's name, but CBC News has independently verified that he is the 18-year-old referred to in the case summary.
The circumstances around some of the deaths remain unknown. In six cases, the coroner classified the manner of death as "undetermined."
One of them is a five-month-old girl who died of "an undetermined cause."
The girl had a history of bed-sharing and a "possible contributing factor of environmental heat exposure."
But that's all the public is allowed to know. The summary doesn't provide the circumstances or history around the case, nor does it reveal the source of the heat the girl was exposed to.
In this case, the child death review committee recommended better followup for babies born to mothers "who consumed drugs or were on methadone during pregnancy."
"Every effort should be made to conduct a home visit to the families of these babies upon discharge," the recommendation says.
It doesn't say whether that home visit happened in this case.
'An undetermined cause'
Another child, a 26-month-old boy, also died of "an undetermined cause."
His death prompted several recommendations around how to handle non-accidental injuries to a child.
The committee called for better information-sharing between hospital emergency rooms and social services, so social workers know when a child has been treated for an injury.
The committee also said children shouldn't be returned to a home where someone injured them when the perpetrator hasn't been identified.
It doesn't say whether this child was returned to a home where he may have been in danger.
"Who is served by secrecy, by keeping information under wraps?" Richard said.
'These stories need to be told'
In British Columbia, where Richard recently left his post as the representative for children and youth, the public is allowed to know the full narrative around what happened to the child.
For comparison, one of Richard's reports, called "Alex's Story," is 71 pages. It tells the story of an 18-year-old Métis youth in care who took his own life.
It details Alex's full history in care, including the number of times the system failed him in some way, from the sexual abuse he endured, and the drugs he was provided with in a group home.
"These kinds of stories need to be told if we're going to improve the system," Richard said.
"Unfortunately, we're still quite timid in New Brunswick in that regard."
Richard said he was "disappointed" by the province's revamped child death review process, describing it as "too modest."
He would like to see the responsibility for child death reviews taken out of the coroner's office and placed in the hands of the current child and youth advocate, who is independent from government.
"The coroner is not an independent office of the Legislature," Richard said. "You're not likely to have full transparency, and we don't."
Chief coroner Gregory Forestell was not made available for an interview.
In an emailed statement, a government spokesperson defended the new child death reporting format.
"The new practice of releasing an anonymized summary of the deceased and circumstances involved with the death has been well received," spokesperson Alexandra Davis wrote.
"This practice effectively provides the public with information about how many child deaths are reviewed, and includes important context for any recommendations."
The government did not respond to a follow-up email, asking who the changes have been "well received" by.
Since 2016, the child death review committee has reviewed at least 24 deaths of children, including five so far this year.
Richard would like to see child protection and child poverty become provincial election issues.