"We are issuing this statement because the community has a right to know that an SFO investigation is under way, but that is all we can say at this time."
The SFO generally deals with cases that involve more than $2 million or if the matter is in the public interest, but it would not say under which of those two categories the FNDC was being looked into.
Mr Brown said neither the council nor SFO had spoken to him about the investigation and it was news to him when the media contacted him yesterday about it.
He was confident that the SFO investigation would not find any impropriety from him during his six-year tenure as mayor.
Mr Brown said there was not enough detail released on what exactly was being looked into, which meant he could not comment on any specifics.
"I do know that the place was crawling with people from the Office of the Auditor General [OAG] for the six years I was there. Every audit [done under his term by the OAG] was clear," he said.
"This has taken me by surprise. I'll be watching closely how things develop, but I'm confident they won't find any impropriety from myself."
Mr Brown said he left the council in a sound financial position, with the lowest debt it ever had at the end of his second term as mayor.