TAIPEI, Taiwan (AP) — China said Tuesday it was pursuing three alleged U.S. operatives accused of carrying out cyberattacks on Chinese infrastructure during the Asian Games held in the city of Harbin in February.

A notice from the Harbin police headquarters named them as Katheryn A. Wilson, Robert J. Snelling, and Stephen W. Johnson and said they worked through the National Security Agency. The police said nothing about how they obtained the names or where the three were believed to be at present.

The alleged attacks targeted the systems for managing the Games themselves, such as registration, competition entry and travel, all of which stored “vast amounts of sensitive personal data of individuals associated with the Games,” the police said.

The attacks continued during the Games in an attempt to “disrupt them and undermine their normal operations,” according to the official Xinhua News Agency.

The report also alleged the NSA cyberattacks targeted critical infrastructure in Heilongjiang province, which includes Harbin, such as energy, transportation, water resources, telecommunications, and defense research institutions. The hackers also attacked Chinese technology company Huawei, Xinhua said.

The report alleged that the NSA “transmitted unknown encrypted data packets to specific devices running Microsoft Windows operating systems within the province.”

The U.S. Embassy in Beijing did not immediately respond to messages seeking comment.

It’s not clear why the alleged attacks would have been timed to the Asian Games, unless it was expected that China might ease some of its strict internet controls while hosting the competition.

The U.S. and China have long accused each other of cyberattacks, with the U.S. also naming Chinese individuals who worked for military hacking units, even issuing wanted posters for them.

Just last month, the Justice Department and others announced coordinated efforts to disrupt and deter the malicious cyber activities of 12 Chinese nationals, including two law enforcement officers, the DOJ reported.

The Office of the Director of National Intelligence last month called China “the most active and persistent cyber threat to U.S. government, private-sector, and critical infrastructure networks.”