The office of special investigations was set up late last year to examine alleged war crimes committed by Defence personnel.

Its director-general, Chris Moraitis, said the office was still months away from making a start.

"We're in the process of engaging investigators and we're going to do that in the next one, two, three months," Mr Moraitis told a Senate inquiry.

"That involves them being sworn in as special members of the Australian Federal Police and involves at least three weeks of induction in preparation, and involves us also doing a few other things."

The office has seconded staff from the home affairs and attorney-general's departments.

It is looking to recruit up to 75 investigators from the AFP and state police forces but Mr Moraitis conceded finding the right people had proven difficult.

The office has spent the past few months sifting through evidence gathered by the Brereton inquiry.

"This process will help ensure investigators will only receive information they can lawfully obtain and use in criminal investigations and any future criminal proceedings," Mr Moraitis said.

"Given the size and complexity of the task, the work of the special counsel is expected to take some time."

Australian Associated Press