Seoul, South Korea (CNN) -- An explosion at a state-run weapons research lab north of Seoul killed one person and injured five on Thursday, South Korea's semiofficial Yonhap news agency reported.
The explosion occurred at the Agency for Defense Development's shooting range in Pocheon around midday, while researchers were testing a shell in a 155-millimeter gun, authorities told Yonhap.
A 40-year-old man died, and two others were seriously wounded, authorities said. Three people with less serious injuries were being treated at a local hospital.
The Ministry of National Defense in Seoul has sent a team of investigators to the facility to determine the cause of the explosion, Yonhap reported.