The US Justice Department has indicted more than 30 North Korean and Chinese individuals on charges of laundering at least $2.5 billion to help fund Pyongyang’s nuclear weapons program, according to an indictment.

The defendants — 28 North Koreans and five Chinese nationals — are accused of using a web of more than 200 shell companies to launder the funds through the international banking system, the Seoul-based Yonhap News Agency reported on Friday citing the New York Times as saying.

The money went to North Korea’s state-owned Foreign Trade Bank and was used to support the country’s weapons of mass destruction program, it said.

The Washington Post called it the largest North Korean sanctions violations case charged by the US.

“The charges alleged in this indictment arise from a multiyear scheme to covertly access the US financial system in spite of sanctions which are intended to deal with unusual and extraordinary threats to the national security, foreign policy, and economy of the US,” said the 50-page indictment by the US attorney for the District of Columbia on Thursday.

North Korea is under multiple layers of US and UN sanctions for its nuclear and ballistic missile programs, said the Yonhap News Agency report.

US-North Korea negotiations to dismantle the nuclear program have made little progress despite three meetings between US.President Donald Trump and North Korean leader Kim Jong-un.