Toshiba CEO to step down in September: sources
Toshiba Corp President and Chief Executive Officer Hisao Tanaka attends a news conference on panel to examine accounting issues in Tokyo May 15, 2015. REUTERS/Issei Kato

Toshiba Corp Chief Executive Hisao Tanaka will step down in September along with other board members including Vice Chairman Norio Sasaki to take responsibility for accounting irregularities, sources familiar with the matter said.

The Japanese conglomerate has hired a third-party committee to investigate past book-keeping practices, and sources have said the probe was focusing on the role top officials played in the irregularities.

Over half of the board was likely to be replaced at the company's next shareholders' meeting in September, sources said on Wednesday, declining to be named because they were not authorized to speak with media.

A Toshiba spokeswoman said the company had not yet made any decision on the matter and was waiting for the third-party committee to release its findings.

The Nikkei business daily earlier reported that Toshiba was expected to announce Tanaka's resignation when the report was released next week.

The laptops-to-nuclear conglomerate first disclosed accounting irregularities in early April, two months after financial regulators ordered a report on past bookkeeping. It has been unable to close its books for the past financial year in the meantime and suspended its year-end dividend.

Sources said previously that investigators' central theory is that executives, worried about the impact of the 2011 Fukushima disaster on its nuclear unit, set overly aggressive targets in new businesses such as smart meters and electronic toll booths, encouraging the understating of costs and overestimating of revenue.

(Reporting by Reiji Murai and Ritsuko Ando in Tokyo; Additional reporting by Abhirup Roy in Bengaluru; Editing by Maju Samuel and Stephen Coates)