A group of men who appeared to be American officials were seen forcing open a back door of the Chinese consulate in Houston on Friday, shortly after a US government closure order for the mission took effect at 4pm Central Time (2100 GMT).
The men did not respond when asked who they were by reporters. Earlier, the same group of men was seen padlocking a door on another side of the building.
After the men went inside, two uniformed members of the US State Department's Bureau of Diplomatic Security arrived to guard the door. They also did not respond to questions from reporters.
The Chinese embassy in Washington and the US State Department did not immediately respond to requests for comment on this activity.
According to a Reuters witness, consulate staff had exited the building shortly after 4 p.m. and left in vehicles before the back door was forced open.