A Samsung investigation into reports of Galaxy Note 7 phones catching fire or overheating has found that some batteries were irregularly sized and that others had manufacturing irregularities, The Wall Street Journal reports. The South Korean firm recalled all 2.5 million Galaxy Note 7 phones last year after repeated complaints. The recall is likely to cost Samsung at least $5 billion and has already affected the company’s brand.

Samsung’s report on the recall, set to be published on Monday, will conclude that the phone’s irregularly sized battery didn’t fit correctly into the Note 7, causing the smartphones to overheat. Unspecified manufacturing issues in replacement phones are also to be blamed for the recall, the Journal reports.

Samsung’s internal Note 7 investigation team worked with a number of outside firms, hiring UL LLC and Exponent Inc to examine the batteries, while TUV Rheinland, a German firm, investigated supply chain issues. The report comes as the firm finds itself embroiled in a corruption scandal in South Korea. Jay Y. Lee, Samsung’s heir apparent, is facing allegations linking him to the country’s widening influence peddling scandal, involving impeached President Park Geun-hye. Lee has denied any wrongdoing.

This story originally appeared on Fortune.com. Copyright 2017