Chinese staff departed China's Houston consulate to a jeering crowd after the U.S. government ordered the building closed, calling it a hub for spying on American companies and researchers.
About 100 protesters shouted "take back China," denounced the ruling Chinese Communist Party (CCP) and waved flags as consulate workers loaded belongings into rental trunks.
The five-story building this week became the latest flashpoint between Beijing and Washington over trade, the novel coronavirus pandemic and military maneuvers in Southeast Asia.
Shortly after the 4 p.m. (2100 GMT) deadline to close the consulate, a group of people were seen by a Reuters journalist using power tools and a crowbar to force open the rear door. They declined to identify themselves to reporters.
After the men went inside, two uniformed members of the U.S. State Department's Bureau of Diplomatic Security arrived to guard the door. They also did not respond to reporters.
The Chinese embassy in Washington and the U.S. State Department did not immediately respond to requests for comment.
According to a Reuters witness, consulate staff had exited the building shortly after 4 p.m. and left in vehicles.
Among the protesters, Zhony Yi Ma, 34, traveled to Houston with a group from New York to heckle consulate staff. Police kept the crowd away from the building.
"We want to end the CCP, take back China and build a nation like America," he said.
Other protesters included a group of supporters of the Falun Gong spiritual group, which is banned in China. Tao Peng, 48, stood silently holding banners calling for an end to communism.
A medical research scientist from Houston, she said the CCP infiltrates groups and cannot be trusted.
"I grew up in mainland China and have seen how the CCP lies," she said as a Falun Gong hired truck circled the area emblazoned on its sides with "Freedom from Communism, and God Bless America."
Senior U.S. officials said on Friday that the consulate was one of the worst offenders in terms of Chinese espionage in the United States and linked its staff to China's pursuit of a vaccine for the new coronavirus.
Nhat Nguyen, 58, praised U.S. President Donald Trump and accused Chinese communists of spying around the world. He wore a Trump 2020 campaign hat and waived the former flag of the South Vietnamese government that was backed by the United States against the communist North in the 1960s-70s era Vietnam war.
"The vaccine is the latest," he said. "They lie, they take," he said.
Consulate staff had duties in eight southern U.S. states. The building closed for official business earlier in the week.
Houston is a major medical hub known for top-notch research on cancer, infectious diseases and since the pandemic hit this year, vaccines for the coronavirus, which first emerged in China late last year. The city is also home to dozens of oil and gas producers that develop technologies used around the world.