Pretoria - Investigations into alleged irregular appointments of senior officials at the City of Tshwane is ongoing, said the Public Protector Busisiwe Mkhwebane.

Mkhwebane said her office had already interviewed mayor Solly Msimanga, speaker Katlego Mathebe and the chief whip Christo van der Heever in connection with the allegations brought to her office by the ANC.

She revealed the status of the investigation during a media briefing at Hatfield on Wednesday.

"We have advanced so much that we have interviewed all the complainants and the executive mayor, the speaker, chief whip and some members of other political parties, especially on the positions of the chief of staff and the spokesperson (of the mayor), city officials and the appointment of the current city manager," Mkhwebane said.

Alleged irregularities in the appointment of the city manager Dr Moeketsi Mosola were highlighted by the ANC's caucus chief whip Aaron Maluleka and the then party deputy, Mapiti Matsena, who formally lodged a complaint with the public protector last year.