A special investigator looking into the financial affairs of Next Digital - the publisher of now-defunct Apple Daily - said on Sunday he thinks his appointment may have to be extended for a fourth time as the probe is still ongoing.

Speaking to reporters after appearing on a radio programme, Clement Chan said that while information gathering was complete, analysis was continuing and he was working on the conclusion.

"Some of the work is yet to be completed. There's a 50 percent chance that the appointment has to be extended," he said.

The former president of the Hong Kong Institute of Certified Public Accountants was appointed by the financial secretary in July last year to investigate the company after allegations of fraud and illegal activities.

Chan's current appointment is due to expire on October 27.

The publisher's founder, Jimmy Lai, as well as several senior editors of Apple Daily have been charged with violating the national security law.