Search for traces of radionuclide or radioactive materials like xenon has been launched by South Korea and the U.S. Saturday after North Korea confirmed it successfully carried out a fifth nuclear test,  the South’s military officials told Yonhap News Agency. Pyongyang’s latest test comes as a response to the international sanctions against the country for its nuclear tests and rocket launch earlier this year

“The investigation team will engage in collecting and analyzing radionuclide exposure in the water and atmosphere,” a military official told the South Korea news agency. The move comes even after the North said no nuclear leak occurred due to the test

The South Korean Air Force dispatched light attack planes outfitted with detectors to estimate the radionuclide level in northeastern Gangwon province’s atmosphere. The navy is tasked with a similar job in the East Sea, the report added. The U.S. military is reported to send a WC-135 radiation detection plane to the East Sea to collect radioactive samples.

The samples of the radioactive materials are reportedly expected to prove helpful in understanding the composition of nuclear substances used the in the reclusive country’s latest test and whether Pyongyang used highly enriched uranium.

On Friday, North Korea’s state TV announced that the country conducted a “nuclear warhead explosion test” to boost its nuclear arsenal. The Kim Jong Un-led country is “now capable of mounting nuclear warheads on ballistic rockets.”

Known to be one of the world’s most secretive countries, North Korea has, in the past, actively carried out nuclear and missile tests much to the anger of South Korea and other world powers. The latest test too attracted flak from the rival neighbor and its allies, the U.S., Australia, France, Japan, Russia and China — the North’s major diplomatic partner.

The United Nations Security Council accused Pyongyang of displaying “flagrant disregard” and “clear violation” of existing U.N. resolutions.

South Korean President Park Geun-hye said that the North’s nuclear test showed that leader Kim was guilty of “maniacal recklessness” in completely neglecting the world’s efforts to bring an end to his nuclear tests.