The defence ministry announced on Wednesday that a South Korean environmental impact assessment of a U.S. missile defense system found “insignificant” electromagnetic radiation relative to safety norms, clearing the route for its permanent deployment.

According to the ministry, the Terminal High Altitude Area Defense (THAAD) system installed in South Korea in 2017 produced electromagnetic radiation at a maximum level that was less than 0.2% of the safety criteria. China and some locals had expressed displeasure with its location in the southeast air base of Seongju.

“The latest environmental impact assessment is a preceding step for the normalisation of the Seongju base,” the ministry said in a statement.

The study result is expected to clear the way for additional infrastructure construction for the system. Officials have said THAAD could not be operated at its full capacity amid protests from nearby residents who raised concerns over the system’s impact on their health.

China has also angrily reacted to the installation, contending that the system’s powerful radar could peer into its airspace.

The United States and South Korea have said THAAD is for self-defence, meant to counter North Korea’s evolving threats.

The nuclear-armed North has been testing various weapons, including its biggest intercontinental ballistic missile, ramping up tension with the South and its main ally, the United States.