Nidec shares slid Monday after the company discovered more suspected cases of improper bookkeeping, heightening fears the world¡¯s biggest maker of mini motors may come under regulatory scrutiny for a potential delisting.

The latest revelations emerged from an external probe that began earlier this month when Nidec found evidence of systemic accounting problems. On Friday, it said in a financial report ¡ª submitted after a three-month delay ¡ª that it had unearthed new problems. Its car inverter business may have for years underreported duties on second-hand goods exported to China, and a Swiss unit may have exported products without completing the required paperwork.

Nidec¡¯s stock fell as much as 4.8% early on Monday, which was also an ex-dividend date for the company. The shares later recouped much of their losses and were down about 1.8% in late morning trading.

¡°Nidec might need some time to rebuild the trust into its financial reporting,¡± Julie Boote, analyst at U.K.-based Japan equity research firm Pelham Smithers Associates, wrote in a report. It has over 300 group companies, and it¡¯s possible that more cases of improper accounting will emerge, given seemingly inadequate internal controls, she added. ¡°The probability of a quick resolution of the accounting crisis is rapidly waning.¡±

Auditor PwC Japan has withheld its signoff on the Kyoto-based company¡¯s securities report for the fiscal year ended March, saying it was unable to obtain enough evidence to form an opinion.

Under Tokyo Stock Exchange rules, any company found to have falsified statements can get labeled a ¡°security on alert¡± and face delisting if the problems aren¡¯t addressed within a year. In the past, that label has been imposed on Toshiba and Olympus, although both avoided getting tossed off bourses.

Governance at Nidec, whose inverters and motors are found in cars, robots, home appliances and data centers around the world, is under scrutiny along with founder Shigenobu Nagamori¡¯s tight grip on the company before he stepped down as chief executive officer last year.

¡°I can¡¯t say all negative factors have been accounted for,¡± Citigroup analyst Takayuki Naito said, noting the auditor¡¯s disclaimer and more findings ahead from a third-party investigation into multiple cases of accounting irregularities. Shares will likely remain sluggish until the third-party committee¡¯s findings are made public, he said.