Samsung’s official investigation into the cause of widespread faults with the Galaxy Note 7 will blame “irregularly sized” batteries and manufacturing faults, according to a report from The Wall Street Journal. The company is set to announce the results of its inquiry this weekend, but the WSJ claims to have revealed its conclusions early, citing information from “people familiar with the matter.”

The WSJ says Samsung hired three independent “quality-control and supply-chain analysis firms” to conduct its investigation, with these firms concluding that two separate faults affected the Note 7.

The first fault relates to devices that used batteries made by Samsung subsidiary Samsung SDI. These batteries didn’t fit inside the phone properly, which led to overheating and, in some cases, explosions. When reports of the Note 7 fault first emerged last August, executives initially believed the problem was confined to these particular devices. In response, they increased production of the Note 7 using batteries made by Hong Kong-based firm Amperex Technology. According to the official investigation, this rush to ensure there was an adequate supply of Note 7 devices for the market led to the second fault — with the increased pressure on production creating unknown “manufacturing issues.”

The Note 7 was recalled globally on September 2nd last year, with this recall followed by a ban of the device on US airlines. On October 11th, after faults continued to be reported in both original and replacement devices, Samsung killed all production and sales of the Note 7. The company says some 96 percent of Note 7 devices have been returned in the US (leaving thousands still in use), and that it has introduced new quality assurances schemes to avoid a repeat of such mistakes in the future.