A panel investigating an accounting scandal at Toshiba Corp. has found that top executives were involved in improper practices, confirming the institutional nature of the abuses, a person directly involved in the investigation said yesterday.

Improper accounting, extended across virtually all business areas of the semiconductor-to-nuclear conglomerate, was part of Toshiba’s “corporate culture,” the person said.

Toshiba expects to take up to $3 billion in charges related to six years of improper accounting, a scandal set to force out chief executive Hisao Tanaka and other company leaders, sources familiar with the matter said this week.

Top officials “received summary reports” from managers on how they were delaying the booking of losses, the investigation source said. Those practices are at the heart of Japan’s worst accounting scandal in five years.

The executives – including Tanaka, vice chairman and former president Norio Sasaki and adviser and former president Atsutoshi Nishida – strongly pressured Toshiba divisions in e-mails and meetings to meet budget targets, worsening the accounting improprieties, the source said.

A company spokesman said he could not comment as the panel’s report has not been released.

The company said yesterday the independent panel, hired by Toshiba after the irregularities emerged in April, will report its findings to the company on Monday, and Toshiba would announce them on Tuesday.

As one measure to prevent a recurrence of the problems, Toshiba is considering naming an outsider to head its Audit Committee, said a Toshiba official familiar with the matter.