The north Belfast storm drain which schoolboy Noah Donohoe entered before he drowned had been inspected the week before he died - but an access hatch to the drain remained unlocked, it's been reported.
BBC NI said a letter written by Infrastructure Minister Nichola Mallon revealed that an inspection of the drain had been carried out on June 18, but no padlock had been fitted.
The St Malachy's College pupil's body was discovered in the drain in the north of the city on June 27 - almost a week after he went missing.
Noah (14) had been travelling to Cave Hill country park to meet friends on the day he went missing.
His disappearance prompted a massive search operation which saw hundreds of volunteers take to the streets in a desperate bid to find him.
Ulster University safety engineer Dr Ciaran McAleenan told the BBC that the metal access grille to the storm drain should always have been locked.
"They are designed to be locked, so clearly it could always have been locked," the academic told the broadcaster.
"In my view it should always have been locked from the moment it was constructed and any safety inspection could have picked that up. The moment it was picked up on inspection, a lock should have been put on it.
"The problem with this particular culvert is that it is open to the public from one end.
"If you are looking at designing a structure of this nature, you should be able to close it completely."
He said that normally, a palisade fence or something similar would totally surround the structure so that it cannot be accessed by the public.
"What we have here is a palisade fence to one end of it - which is locked - but at the opposite end it is totally open," Dr McAleenan told the BBC.
"I would have this fenced off completely immediately."
In the weeks after Noah's death, there was intense speculation about what might have happened to him.
But in a preliminary hearing two weeks ago into the death of the schoolboy, Coroner Joe McCrisken said that there was currently "no evidence" to suggest that any other person was involved in Noah's death.
The Coroner said that he wanted to set out "fact against fiction" in order to "dispel the many baseless and inaccurate rumours which continue to circulate".
Police believe Noah entered the drain in the Northwood Road area of north Belfast.
He had cycled there from his home in south Belfast and, shortly before he went missing, was seen with no clothes on.
Prior to that he was seen falling off his bike on the Shore Road.
The coroner described the drain as running underground from Northwood Road to Shore Road to Seaview, under an access road at a Translink cleaning facility, and under the M2 motorway before discharging close to Duncrue Road.
"Noah's body was found by specially trained police officers between two drain access points within a section of the tunnel running under the Translink access road," said Mr McCrisken.
"The environment within the drain system can be described as challenging, with the drain system backfilling with water during intervals between low and high tides.
"I consider that, based upon all of the evidence before me at this stage, and the evidence includes extensive CCTV footage and witness statements, that Noah acted alone when he travelled to Northwood Road and entered the drain system."
At the hearing the Coroner said he had reassured Noah's family that further evidence will be assessed as it is received.
"But that is my preliminary view based upon the evidence that is before me presently.
"At present there is no evidence linking Noah's death to the death of any other individual or with an attack on any other individual or individuals in that area or in close proximity to Northwood Road.
"There is no evidence at present to suggest that any other person was involved in Noah's disappearance and death."
A further preliminary hearing is scheduled for November 2.
A full inquest is due to be heard on January 18 next year.