Last month in the Mexican state of Chiapas, near the Guatemalan border, Mexican police (the federal PFP and Chiapas state border cops) stopped a a truck and discovered 169 Central American illegal aliens in its trailer.
The Central Americans included 26 children and a 15-year old girl who was 5 months pregnant. Nationally speaking, 161 were from El Salvador and 8 from Guatemala, both countries poorer than Mexico.
Apparently the illegal aliens weren't keen to vacate the trailer. In order to get them out, Mexican police gassed the trailer, and the Central Americans got out.[ Revisar?? Segob plan para endurecer trato a ilegales regresar, El Siglo De Torreon, April 17 2006]
I assume the gas they used was CS (tear gas), which I've been exposed to as part of training in the U.S. Army.
Can you just imagine the outcry that would ensue if U.S. immigration officials used gas on Mexican illegal aliens?