“Issues within our terms of reference are numerous and complex,” the committee said on Tuesday.
“More time is required for it to analyse and study the large amount of information submitted by various parties.”
The committee was set up by the chief executive on December 12 last year to review the cause of the fire and recommend measures to prevent similar incidents.
It formally began work on December 19.
Since then, it has conducted site visits to the buildings, heard 30 days of oral testimony from 80 witnesses, and examined expert reports and legal submissions.
The committee said it continues to process more than one million files of written evidence and other materials that are still being received, while the drafting of the report has begun.
Under the original timeline, the committee was expected to complete its report within nine months.
But with the huge amount of information gathered, it requested — and received — the chief executive’s backing for an extension.
The committee now expects to submit its final report by the end of October.
It said it would continue its work “in accordance with the principles of fairness, openness and impartiality”, and would carefully consider every item of information received before finalising its findings.