Fri May 22, 2015 12:21am EDT

Japan industrial conglomerate Toshiba Corp said on Friday it would investigate accounting practices in its TV, computer and chip businesses, extending a probe already under way into irregularities that led to profits being overstated by at least $415 million in recent years.

The move comes after Toshiba last week set up a third-party committee, headed by a former prosecutor, to conduct an independent inquiry in addition to its own internal investigation into accounting problems related to infrastructure and construction work.

Toshiba said previously it was likely to mark down operating profit by at least 50 billion yen ($415 million) for the three years through March 2014 after it found inappropriate reporting of some infrastructure project costs and construction work.

Shares of Toshiba, whose businesses extend from laptop computers to nuclear power plants, have slid about 20 percent since it disclosed the latest scandal in early April. The stock turned higher after Friday's statement, and was up 0.7 percent in Tokyo, outpacing the broader market, which was flat.

The accounting probe - the second at the company in less than two years - has forced Toshiba to delay reporting its earnings for the fiscal year ended in March. On Friday, Toshiba said it plans to release earnings as soon as possible after the probe is complete.