The district councillors whose oaths are being put under the microscope include former lawmaker James To from the Democratic Party, and the party’s vice chair, Edith Leung.
The oath of barrister Lawrence Lau, who’s been charged with violating the national security law over the Legislative Council primaries, has also come under scrutiny.
The ten district councillors have been told to submit further information to Tsui, so he can decide on the validity of their oaths.
Sham Shui Po district councillor Lee Man-ho has already been unseated for not attending the oath-taking ceremony in North Point.
The oaths of the other 45 district councillors who attended the ceremony have been declared valid.
Earlier this month, the authorities disqualified seven out of 24 Hong Kong Island district councillors who attended a similar oath-taking ceremony.