(Reuters) - The United States and China are targeting the finances of Hongxiang Industrial, a Chinese company headed by a Communist Party cadre which the Obama administration thinks has a role in assisting North Korea’s nuclear program, the Wall Street Journal reported on Monday. Police in Liaoning, the northeastern border province of China, started a probe into the firm's alleged long-term involvement in "serious economic crimes" over the course of its trading activities, the paper reported. (on.wsj.com/2cz8iu1) Certain assets related to the company, its founder and top executive Ma Xiaohong, and some of her relatives and associates, have been frozen by the Chinese authorities in recent weeks according to the government and corporate filings cited in the report. U.S. Department of Justice prosecutors visited Beijing twice last month to make their Chinese counterparts aware about alleged criminal activities being committed by Hongxiang Industrials, it said. The Justice Department is preparing as early as this week to announce legal action against Chinese firms suspected of providing financial assistance to Pyongyang, the Journal reported, citing officials familiar with the matter.  U.S. President Barack Obama and Chinese Premier Li Keqiang agreed on Monday to step up cooperation in the United Nations Security Council and in law-enforcement channels after North Korea’s fifth nuclear test, the White House said. The U.S. Congress passed legislation this year that would sanction anyone who engages in, facilitates or contributes to North Korea’s proliferation of weapons of mass destruction. Representatives of the U.S. Department of Justice, Chinese Government and Hongxiang Industrial were unavailable for immediate comment. 