South African retail group Steinhoff, which is fighting for survival following its disclosure of accounting irregularities, said tycoon and major shareholder Christo Wiese has stepped down as chairman.

Steinhoff said in a statement on Thursday that Wiese had offered to resign to reinforce independent governance of the company and that the supervisory board had accepted his resignation “to address any possible conflict of interest that may exist”.

The company said that Heather Sonn, a member of the supervisory board and its independent sub-committee, had agreed to assume the position of acting chairperson, adding that Wiese’s son Jacob had also resigned from the board.

Steinhoff rapidly expanded to own more than 40 retail brands around the world including Conforama, Mattress Firm and Poundland, but its share price has plummeted since it announced last week that it had found problems with its accounts and its chief executive had quit.

South African state pension fund, PIC, the second-largest investor in Steinhoff after Wiese, said on Wednesday it would ask for a seat on the board committee investigating accounting irregularities at the company.

The Public Investment Corporation (PIC), which has about 10 percent in Steinhoff, had said there was the risk of a possible conflict of interest in having Wiese serve as interim CEO after the departure of Markus Jooste, and it wanted the appointment of at least two independent non-executive directors.

Steinhoff, which moved its primary share listing from Johannesburg to Frankfurt two years ago, has been under investigation for suspected accounting irregularities in Germany since 2015. Four current and former managers are under suspicion of having overstated revenues at subsidiaries, prosecutors said.

Steinhoff has previously said that the investigation related to whether revenues were booked properly, and whether taxable profits were correctly declared.

Steinhoff and grocery retailer Shoprite called off a deal in February to create an African shopping giant, preventing Wiese, who has stakes in both companies, from bringing more of his retail assets under one roof.

He started budget clothing retailer Pepkor in the 1960s, in Upington on the southern edges of the Kalahari desert, but is best known for transforming Shoprite from just six shops in the 1970s to hundreds of stores across Africa.