More than a dozen members of the U.S. Congress have written to America’s top prosecutor demanding to know the full extent of alleged influence and espionage activities carried out by diplomats and agents of China in the United States, Newsweek has learned.

In a letter reviewed exclusively by Newsweek, sent last week to Attorney General Merrick Garland and to the head of the FBI Christopher Wray and Secretary of State Anthony Blinken, the 13 lawmakers warned of “systemic influence operations from our principal geopolitical adversary”—China—and said the U.S. government was not responding adequately to the challenge.

The lawmakers, led by Rep. Darrell Issa (R-CA), pointed to what they said were “blatant and repeated instances of People’s Republic of China (PRC) diplomats and their recruited allies in America undertaking activities and campaigns that targeted—often violently—American citizens exercising their First Amendment rights.”

In two examples, they highlighted the indictment in early September of Linda Sun, a former New York official, whom the Justice Department alleges was working as an unregistered foreign agent on behalf of the Chinese Communist Party, in coordination with four diplomats at the Chinese consulate in the city. Sun has pleaded not guilty.

The lawmakers said pro-CCP forces had committed “nothing short of criminal assault” against democracy activists in San Francisco last year as Chinese leader Xi Jinping and President Joe Biden met at the APEC summit.

Newsweek‘s reporting has shown extensive infiltration of U.S. civil society by the CCP’s “united front” campaign, a political tactic that attempts to treat ethnic Chinese everywhere as potential agents of influence, who can be turned to work for Beijing. While some targets knowingly help the CCP, others do not—while still others may not be aware of what is happening.

In 2020, Newsweek documented some 600 organizations belonging to this sprawling influence and interference network in the United States. Last year, Newsweek‘s research found dozens of groups and their leaders had been actively participating in local elections in New York state for decades.

In their letter, the members of Congress asked the State Department to explain why it did not expel Huang Ping, China’s consul general in New York, whose office was named in the DOJ indictment of Sun, the former deputy chief of staff to New York Gov. Kathy Hochul.

After the indictment was unsealed on September 3, State Department spokesperson Matthew Miller said Huang had “rotated out of the position” at the end of August as scheduled.

Yet as late as September 21, the senior diplomat was presiding over a reception for approximately 700 mostly ethnic Chinese residents from the 10 northeastern U.S. states that the consulate serves. Huang thanked them for their loyalty and delivered patriotic remarks for China’s National Day, which falls on October 1, according to the consulate’s website.

Huang was no longer in the U.S. as of September 27, according to a source with knowledge of the matter. China’s New York consulate could not be reached for comment.

A State Department spokesperson told Newsweek: “We have made clear that it is unacceptable for foreign governments to engage in conduct involving violations of U.S. law by U.S. citizens.”

Huang, who was not personally named in the indictment, “should have been on a plane weeks ago, but instead lingered in New York City doing one victory lap after another over America’s national interest,” Jonathan Wilcox, a spokesperson for Congressman Issa, said in a telephone interview.

All 13 lawmakers who signed the letter are Republican, but Wilcox said it was not a partisan issue. “It is not just a bipartisan issue, it’s a nonpartisan issue of mainstream government and national interest concern.” “This is obviously a law enforcement matter,” he added.

In April, FBI Director Wray said that risks posed by the Chinese government to U.S. national and economic security were “upon us now.”

In the past, China’s embassy in Washington, D.C., has said it follows U.S. law and has denied it engages in united front influence and interference or espionage activities. The embassy did not reply to an emailed request for comment.

In an extensive emailed statement to Newsweek, the FBI said counterintelligence and economic espionage efforts emanating from China and its ruling party were “a grave threat to the economic well-being and democratic values of the United States. Confronting this threat is the FBI’s top counterintelligence priority.”

“When China violates our criminal laws and international norms, we are not going to tolerate it, much less enable it,” the FBI said, adding it “conducts logical, fact-based investigations and follows the evidence wherever it may lead.”

The issue was not about ethnicity, but about politics and national security, the FBI said. “To be clear, the adversary is not the Chinese people or people of Chinese descent or heritage. The threat comes from the programs and policies pursued by an authoritarian government.”

In their letter, the U.S. lawmakers demanded a classified briefing from Garland, Wray and Blinken to answer questions including the “current counterintelligence understanding” of operations run by China’s State Security Ministry and the CCP’s United Front Work Department in the United States.

“What is the U.S. Government’s strategy to bring the mass of these operations to an end?” another question read.

Others still focused on the role of Chinese diplomats: “Why was Huang Ping not expelled in conjunction with the Justice Department unsealing the indictment against Ms. Sun?”

A former government official who has worked on U.S.-China relations, and who spoke anonymously due to political sensitivities, said the State Department did not expel Huang as it was afraid of causing a tit-for-tat expulsion of American diplomats from China.