International flights to Beijing were being stopped before they reached the -terminal and were not allowed to offload until health authorities had checked passengers and crew for symptoms, airport officials said yesterday.

Mexican citizens showing no signs of illness were being singled out during these health checks, no matter where the aircraft were from, and taken away for quarantine in hospitals and hotels without explanation and without embassy or consulate staff being informed, Mexican officials said.

In one case, a Mexican citizen living in Beijing was taken off an aircraft on returning from a business trip to New York and put into quarantine in a state-run hotel near his home, despite showing no flu symptoms and despite not having gone to Mexico, according to Mexican officials who asked not to be named. They said no passengers of other nationalities from his aircraft were quarantined despite being in close contact with him on the flight.