Deputy First Minister Michelle O'Neill has said she raised with the chief constable concerns over "due diligence" in the police investigation into the death of Noah Donohoe.
The 14-year-old's body was recovered from a storm drain in North Belfast in June, six days after he went missing.
Ms O'Neill last week said she had raised during a meeting with Simon Byrne her "grave concerns" over the PSNI's handling of the investigation.
In an interview with Belfast Live, the Sinn Fein deputy leader said she put a number of questions to the chief constable and plans to follow this up in writing.
Ms O'Neill again expressed her sympathies with Noah's mother Fiona.
The Deputy First Minister said: "I have concerns about the police investigation. That's as a direct result of my ongoing communication with both the family and also with the legal team.
"So I put a number of questions to the chief constable, and which I am also going to follow up in writing.
"Because I do think that the family deserve to have all the answers and every piece of information, and they're right to ask questions whenever they are not satisfied with the approach.
"Without going into too much detail, I just think that it's important that I register at the highest level of the PSNI our concerns in terms of what we perceive to be a lack of perhaps due diligence across a number of areas, and I'll continue to work with Fiona, with the family and with the legal team."
Ms O'Neill declined to elaborate on the concerns she had or what questions she felt remained unanswered, due to ongoing investigations.
She said: "In respect to the investigation, I think it's important that I don't get into that because I don't want to do that on the public airwaves.
"But just to say, the concerns that the family have are the concerns which I have expressed to the PSNI.
"And I will continue to work with Fiona and with the legal team to try to get to the bottom, and to get them the answers which they obviously deserve.
"It's just been a harrowing experience for any parent to go through.
"Our thoughts are always with Fiona. We work every day to try and get her the answers that she deserves and that Noah deserves."
Noah's disappearance prompted a major search operation involving hundreds of volunteers.
The PSNI last year said they believed the schoolboy entered the storm drain in the Northwood Road area.
He had cycled to the area 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.
An inquest into the teenager's death is scheduled for next year.
