Most of the Royal Commission into the Christchurch mosque attacks may be held behind closed doors.
The inquiry officially started yesterday.
Commissioners Justice Sir William Young and former diplomat Jacqui Caine are now considering evidence.
In an eight-page document issued yesterday, the commission said it was considering whether its evidence gathering process would be held entirely in private.
It said allowing the public to hear details of intelligence agencies carries the risk of providing a "how to" manual for potential terrorists.
It also did not want to interfere with the right to a fair trial for the accused man.
A commission spokesperson said it was possible evidence from the police, Immigration New Zealand and customs could be heard in public.
One or more public forums could also be held, but what those look like is yet to be decided.
Anjum Rahman from the Islamic Women's Council said she expected evidence that could interfere with the accused's fair trial right to be heard privately.
But the rest, she said, should be open to the public.
"Engagements of the government, and government departments, with Muslim communities and what happened to preventative measures and why those didn't go ahead. . . those parts of the inquiry should be able to be held in public and in a more transparent way."
The commission is expected to report back to the governor general in early December.