BEIJING (Reuters) - The United States will not tolerate any pressure from the Chinese government on family members of fugitives to get them to return from America, but can’t guarantee it has not happened, a U.S. official said on Tuesday.

Yang Xiuzhu reads a newspaper during a meeting in Wenzhou, Zhejiang province, December 29, 2001. REUTERS/Stringer

China’s most-wanted graft suspect, Yang Xiuzhu, gave herself up and returned from the United States last week in a major victory for the ruling Communist Party’s overseas hunt for fugitive officials.

Beijing has pursued a search dubbed Operation Fox Hunt for corrupt officials and business executives who have fled abroad with their assets, part of President Xi Jinping’s war on deep-seated corruption.

Upon Yang’s return, the government said family members had cut off funds and were lobbied by senior members of the Chinese community in the United States as part of efforts to secure her surrender.

Yang, a former deputy director of Wenzhou’s construction bureau in the booming eastern province of Zhejiang, spent 13 years in hiding abroad.

A U.S. official, speaking to reporters in Beijing under condition that neither names nor government departments were mentioned, said they had been clear with their Chinese counterparts on the repatriation process.

“We’ve made clear that we will not tolerate any pressure being placed on family members or otherwise as a basis for return and ... we can’t always ascertain that that’s been lived up to,” he said.

Asked if there were specific U.S. concerns about Yang’s case, the official said: “If we had proof that they had engaged in conduct that violated the ground rules we’ve set, of course we would make our objections clear and would not permit that to go forward.”

“It’s not that we’re saying that family members can’t contact someone and suggest it would be better for them to come back. What we’re saying is that the Chinese can’t - no country should be allowed - to put pressure on other individuals, family members or otherwise, to secure a return,” he said.

It has not been possible to reach Yang or a legal representative in China for comment.

In April 2015, China published a list of 100 of its most-wanted corruption suspects, many living in the United States, Canada and Australia.

China has upset Western countries by sending undercover agents to try and get suspects back, although it says it has changed tactics after complaints.

“Any law enforcement activity by Chinese law enforcement in the United States of America must be done with the knowledge and concurrence of the United States government and its law enforcement entities,” another U.S. official said.