Investigators believe the latest incidents of  Samsung smartphones overheating, which prompted it to abandon its Galaxy Note 7 model, may be the result of a flaw different from the one that caused the device’s original recall last month, according to Bloomberg.

Preliminary examination of the evidence from recent battery incidents suggests there is an issue with the batteries made by China’s Amperex Technology, which were supposed to be a safe alternative to those supplied by another company that led to scores of incidents in which phones burned and melted, according to a person familiar with discussions between government agencies and the company.

The issue may have crept into the supply line after Samsung began replacing Note 7 phones that were equipped with batteries made by Samsung SDI, said the person, who wasn’t authorized to speak publicly about the issue. The SDI batteries were slightly too large for the phone, according to a U.S. consumer-safety agency. Samsung is a major shareholder in Samsung SDI.

The apparent new fault helps explain why Samsung would abruptly pull the plug on what was supposed to be its premier phone designed to compete against Apple Inc.’s iPhone 7. Amperex, a unit of Japan’s TDK, didn’t respond to requests for comment while Samsung declined to comment.