The US government secretly expelled two Chinese Embassy officials this fall after they drove onto a sensitive military base in Virginia, according to people with knowledge of the episode. The expulsions appear to be the first of Chinese diplomats suspected of espionage in more than 30 years.

US officials believe at least one of the Chinese officials was an intelligence officer operating under diplomatic cover, said six people with knowledge of the expulsions. The group, which included the officials’ wives, evaded military personnel pursuing them and stopped only after fire trucks blocked their path.

The episode in September, which neither Washington nor Beijing made public, has intensified concerns in the Trump administration that China is expanding its spying efforts in the US as the two nations are increasingly locked in a geopolitical and economic rivalry. US intelligence officials said China poses a greater espionage threat than any other country.

The expulsions show the US government is now taking a harder line against suspected espionage by China, officials said.

Recent episodes of suspected spying add to the broader tensions between the United States and China, the world’s two largest economies and biggest strategic rivals. That conflict is heightened by a trade war that President Donald Trump started in July 2018 and that shows only tentative signs of abating.

China destroying Uighur burial grounds Show all 6 1 /6 China destroying Uighur burial grounds China destroying Uighur burial grounds Teywizim cemetery in Hotan (before and after) China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 29, 2017 (top) showing a cemetery (C) and the same view on July 5, 2019 (bottom) with no sign of the facility in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds A graveyard in Aksu (before and after) An image of a graveyard in Aksu in 2015, where Uighur poet Lutpulla Mutellip was buried and the same view in 2018 and then again in 2019 showing a new park called "Happiness Park" Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 29, 2017 (top) showing a cemetery (C) and the same view on July 5, 2019 with no sign of the facility in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds Sulanim cemetery in Hotan (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from April 24, 2018 (top) showing the Sulanim cemetery (C) in Hotan, Xinjiang province and the same view on August 6, 2019 (bottom) with no sign of the facility and it has been replaced with a car park. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 20, 2014 (top) showing a cemetery (centre L) and the same view (bottom) on July 5, 2019 where it has been replaced with a a newly built standardised cemetery, in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty

The base intrusion took place in late September on a sensitive installation near Norfolk, Virginia. The base includes Special Operations forces, said people with knowledge of the incident. Several bases in the area have such units, including one with the headquarters of the Navy’s elite SEAL Team Six.

The Chinese officials and their wives drove up to a checkpoint for entry to the base, said people briefed on the episode. A guard, realising that they did not have permission to enter, told them to go through the gate, turn around and exit the base, which is common procedure in such situations.

But the Chinese officials instead continued onto the base. After the fire trucks blocked them, the Chinese officials indicated that they had not understood the guard’s English instructions and had simply gotten lost.

It is not clear what they were trying to do on the base, but some US officials said they believed it was to test the security at the installation.