The South Korean government began its own investigation into battery fires in Samsung Galaxy Note7 smartphones, officials said.

Samsung Electronics Co., a South Korean company and the world’s largest phone maker, ended production of the smartphone last week after a global recall, and after reports that both the phone’s original and replacement batteries were catching fire.

The state-run Korea Testing Laboratories began its own investigation Thursday on five phones provided by Samsung, which caught fire in South Korea. Industry officials said KTL will not limit its probe to only the batteries, but will use technologies including X-Ray and computerized tomography to study the entire phone. Company officials said Samsung is also considering testing defective smartphones collected by the U.S. Consumer Product Safety Commission, which ordered two rounds of recalls for phones sold in the United States.

Finding the cause of the Note7’s problems is crucial in winning back customer loyalty before Samsung’s Galaxy S8 is released in 2017. Samsung’s stock price declined in Asian markets after the announcement of a halt to production, and the company reduced its third-quarter profit forecast, as well as forecasts for the next two quarters.