More than 150 Mexican citizens donning facemasks were sent under quarantine in ambulances to four Chinese airports to fly back home on a chartered flight.

An AeroMexico chartered flight?-- which earlier picked up passengers quarantined in Shanghai, Beijing and Guangzhou?-- took off from Hong Kong International Airport late last night heading to Mexico City, the center of the H1N1 flu outbreak.

The charter flight was part of an agreement between the Chinese and Mexican governments to transport citizens of both countries back home.

In Mexico City yesterday, 79 Chinese citizens boarded a Boeing 777-200 jet that took off from Benito Juarez international airport. The flight was headed for Tijuana, the northern Mexican city near the US border, to pick up more Chinese, 200 in all, before their scheduled return to Shanghai at 10am today.

The 17-member Chinese Southern Airline crew, which includes a quarantine expert, have been trained on precautions against the virus and will monitor the conditions of the passengers every step of the way.