Samsung Electronics said Monday that faulty battery caused its flagship Galaxy Note 7 to catch fire after discontinuing the fire-prone device more than three months ago.

In a special press conference in its headquarters in Seoul, Samsung said that a mix of thin separators between the positive and negative layers, abnormal squeeze in battery corners, abnormal bump in battery surface and absent insulating tape caused the Note 7s to explode and set on fire.

The findings are based on two investigations by U.S.-based firms UL and Exponent, which examined batteries and one supply-chain analysis by a German company TUV Rheinland.