"At least three people were killed by an ammonia gas leak from a pipeline owned by state oil monopoly Pemex in southern Mexico on Tuesday and 1,500 people were evacuated from the area and taken to shelters, the company said."

"Mexican media put the death toll at four and said some 40 others were poisoned by the leak in the southern state of Oaxaca.

Pemex said the leak was caused when the pipeline was damaged by heavy machinery operated by a private company doing road work.

Pemex has had a poor safety record in recent years."
 
Miguel Gutierrez reports for Reuters August 22, 2013. [2]