By Se Young Lee SEOUL (Reuters) – A Samsung Electronics Co Ltd investigation into what caused some Galaxy Note 7 smartphones to catch fire has concluded that the battery was the main reason, a person familiar with the matter told Reuters on Monday. Investors and analysts say it is critical for Samsung to provide a convincing and detailed explanation about what went wrong with the Note 7 and how it will prevent such problems from recurring if it is to regain consumer trust. "They've got to make sure they come clean and they've got to reassure buyers as to why this won't happen again," said Bryan Ma, Singapore-based analyst for researcher IDC.