TOKYO, May 15 (Reuters) - Toshiba Corp announced on Friday it had appointed a third-party committee, headed by a former prosecutor, to probe accounting irregularities that overstated operating profits by at least $420 million in recent years.
The industrial conglomerate spooked investors last week, saying it was extending an investigation into inappropriate reporting of some infrastructure project costs and construction work. It said this week the irregularities may mean it has to mark down three years of profit by about 7 percent.
To buttress an internal probe, Toshiba appointed a panel of four outsiders, headed by Koichi Ueda, a lawyer and former head of the Tokyo High Public Prosecutors Office, as well as another lawyer and two accountants.
Toshiba said it does not yet know the scope or time frame for the third-party investigation and that it will not report earnings for the year ended in March until that probe is complete.
But it said it will "disclose any material information, if found" by either probe as soon as possible.
Toshiba's second accounting investigation in less than two years had provided unwelcome echoes for some in the Tokyo market of previous probes that billowed into major corporate scandals. In the highest profile case in recent years, camera and medical equipment maker Olympus Corp in 2011 admitted to a 13-year cover-up that hid $1.7 billion in losses. (Writing by William Mallard; Editing by Muralikumar Anantharaman)