North Korea remains at the bottom of a major ranking of nuclear materials security conditions, a nonprofit group of experts here said Wednesday. The Nuclear Threat Initiative (NTI), which is working to curb the threat of nuclear terrorism and accidents, released the results of a survey of 25 countries with one kilogram or more of weapons-usable nuclear material. It was conducted with the Economist Intelligence Unit (EIU) The NTI ranked North Korea 25th, giving it just 30 points out of the total 100. It took into account the amount of nuclear materials, sites, domestic commitments, societal factors and global norms. "North Korea ranks last in the NTI Index, with its score unchanged compared to 2012," the Washington-based organization said. The NTI, however, pointed to a lack of credible information on the secretive communist nation's nuclear program. In 2008, during talks with the U.S., the secretive North reportedly declared that it possessed 38.5 kg of plutonium. "The lack of available information on North Korea's nuclear security -- it does not publish its nuclear security laws and regulations or other information -- meant that North Korea received the lowest possiblescore for several sub-indicators," it said. If North Korea were to publish its nuclear security laws and regulations or other information about its nuclear security or its materials stocks, its score in a future edition of the NTI Index might improve, said the NTI. "North Korea could also improve by signing and ratifying key international agreements and participating in international nuclear security initiatives," it added.