TOKYO: Ratings agency S&P warned Tuesday that Nissan faces a possible debt downgrade after its chairman Carlos Ghosn was arrested for alleged financial misconduct. S&P Global Ratings announced a “CreditWatch with negative implications” and said it “also placed all of our ratings on Nissan’s overseas subsidiaries on CreditWatch negative.” It warned the firm’s profitability could “weaken substantially” in fiscal years 2018 and 2019 if Ghosn’s alleged misconduct affected Nissan sales or hurt its alliance with Renault and Mitsubishi Motors. It said any downgrade “is likely to be by one notch.” “Although Nissan said it aims to identify its governance issues and hammer out preventive measures, we think rebuilding its management culture swiftly will not be easy.” Auto titan Ghosn, who headed the automaker alliance, was arrested in Tokyo on Monday on allegations that include systematically under-reporting his income. His detention marks a stunning fall from grace for the Brazil-born executive who is credited with resurrecting Nissan through bold restructuring measures. Ghosn has yet to comment on the allegations against him. Nissan’s board is set to meet on Thursday to discuss dismissing him.