The Chinese officials and their wives drove up to a checkpoint for entry to the base, said people briefed on the episode. A guard, realizing 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 on to the base, according to those familiar with the incident. 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, according to people briefed on the matter.

American officials said they were skeptical that the intruders made an innocent error and dismissed the idea that their English was insufficient to understand the initial order to leave.

It is not clear what they were trying to do on the base, but some American officials said they believed it was to test the security at the installation, according to a person briefed on the matter. Had the Chinese officials made it onto the base without being stopped, the embassy could have dispatched a more senior intelligence officer to enter the base, the theory goes.

The Chinese Foreign Ministry and Chinese Embassy in Washington did not reply to requests for comment about the episode. Two associates of Chinese Embassy officials said they were told that the expelled officials were on a sightseeing tour when they accidentally drove onto the base.