The Law Society on Monday said it is looking into an allegation by national security police that a number of lawyers have committed professional misconduct.

It said police made a complaint after looking into a case related to the now-defunct 612 Humanitarian Relief Fund that raised money for the legal and medical fees of anti-government protesters.

At a press conference on Monday, Law Society president CM Chan said they have set up a three-person investigation committee to probe the complaint.

But he refused to divulge further details, such as what kind of misconduct is suspected and how many lawyers are allegedly involved.

"We're unable to disclose any information because the nature of our conduct investigation is highly confidential. It is only fair to the [respondents] and those who made the complaint that we don't disclose any details at this stage," he said.

"We will, at an appropriate juncture, increase transparency to let the public know the details of our investigation."

The society said if warranted, the committee will refer the matter to the Solicitors Disciplinary Tribunal, which has the power to strike-off lawyers.

Five trustees of the relief fund, including Cardinal Joseph Zen and barrister Margaret Ng, were arrested earlier this month on suspicion of conspiracy to collude with foreign powers to endanger national security.