Faulty batteries and manufacturing problems were likely the main cause of the Samsung Galaxy Note 7s catching fire, a South Korean government agency has said.
The Korea Agency for Technology and Standards (KAT), which conducted its own investigations, said it found many highly probable causes in the batteries of the recalled phones. It added that it didn't find any likely cause from the smartphone itself.
It is the same conclusion as the one reached by Samsung last month, when it was officially announced that faulty batteries were to blame for the fiasco.
KAT ordered state-backed Korea Testing Laboratory to conduct tests. It organized 13 experts in hardware, programming, and batteries who met weekly to supervise and research test results.
The lab tested 14 of the phones that caught on fire, 46 of the models that didn't catch fire, and 169 of the batteries. It also received from Samsung two smartphones and two batteries that expanded more than others.
After analyzing the damaged models, the lab said circuit damage was concentrated around the battery.
Specifically, looking into the batteries themselves, KAT said batteries of manufacturer B -- China's ATL -- that were not damaged had a protruding anode tab as a design flaw. The protrusion caused the separators to rip and come into contact with cathode materials that then caught fire. Insular tapes were also missing in some of them.
This particular design flaw was not found on the Galaxy S7 Edge, which also used ATL-made batteries.
For manufacturer A -- Samsung SDI -- there was a design flaw where the round corners of the battery pressed into the negative board, causing fires.
Other tests focused on the smartphone itself, and whether safety measures native to the Note 7 actually worked. KAT intentionally overcharged the phone and damaged the circuits protecting the battery, neither of which were found to cause fires.
The lab said protection software for controlling temperature worked correctly on the smartphones, and found that no external pressures caused the batteries to catch fire either.
The lab also said that the Galaxy Note 7 had the same additional space ratio -- given to allow the batteries to expand -- as the Galaxy S7 Edge, making it more unlikely that smartphone design was the cause of the fires.
KAT said that if Samsung had strengthened its manufacturing and quality control beforehand, the disaster could have been prevented. It added that it will improve the current recall regulations and safety standards for batteries and handsets going forward.