The world’s top smartphone maker Samsung examined its Galaxy Note 7 disaster and found that the explosion of its phones was caused by defective batteries.

Galaxy Note 7 was launched in August 2016, and it was considered as a rival to Apple’s iPhone and on September 2016 Samsung received complaints of overheating and exploding batteries, and had to recall 2.5 million phones, it costs a damage of around $5.3bn to the company.

Investigation concluded that the reason for the explosion and overheating was due to bad battery design and a hurry to release an updated version of the Galaxy Note 7, said by Samsung in a report on Sunday night. The phones that were launched in August had battery too large for the phone casing.

The recalled phones were manufactured with a battery from a different supplier but it showed the same problem. So Samsung recalled all the Note 7 phones and cancelled the product.

At a press conference, the head of Samsung smartphone business apologised on behalf of the company.