A 21-year-old man is in a coma and eight party-goers have been treated in hospital after liquid nitrogen was poured into a swimming pool.
The event occurred at a pool party organised for spirit company Jägermeister on Saturday in Leon, Guanajato, Mexico.
Amateur video shows the moment four large buckets of liquid nitrogen were poured into the pool, sending a haze of smoke into the air and causing some guests to pass out.
Guests leaped into the water to save party-goers overcome by the toxic gas
Jael Jimenez, a hostess at the party, said: “They realised that I had fainted because the saw the tray floating alone in the pool, otherwise I might have drowned," The Sun reports.
It is believed staff had hoped the chemical would simply cause a smoky effect, though chemistry blog ChemBark writes: "Nitrogen quickly boils and displaces all of the oxygen present, causing people in the area to asphyxiate."
The blog, authored by Harvard chemistry graduate Paul Bracher, adds: "Nitrogen gas is relatively inert and will not react with anything present in the pool. The danger is simply from nitrogen pushing away all of the oxygen around, leaving no oxygen for the swimmers to breathe."
Jose Ignacio Lopez del Toro remains in a coma, Univision Noticias states.
The attorney general has launched an investigation into the event, after four of the injured guests filed criminal complaints, Mexican newspaper El Universal writes.
The party was organised for spirit company Jägermeister on Saturday in Leon, Guanajato, Mexico
A Jägermeister spokesman told The Telegraph: "We are aware of this incident in Leon, Mexico, which is currently being investigated by our headquarters here in Germany.
"We are liaising with the responsible distributor in Mexico who is working with the event organisers and the investigating authorities to understand the full circumstances surrounding the events last Saturday night.
"We fully support responsible drinking and adhere to the guidelines within each market in which we operate."
Liquid nitrogen is sometimes used in cocktails and can be extremely dangerous if not handled properly.
Emergency operation: Gaby Scanlon
Last year British teenager Gaby Scanlon had been out celebrating her 18th birthday with friends when she developed severe stomach pain after drinking a cocktail with liquid nitrogen in it.
She later had to have emergency surgery which saw part of her stomach removed.
According to the Food Standards Agency (FSA), the chemical is not a toxic substance, although it is not safe to drink or eat.
Liquid nitrogen is used to quickly chill or freeze food. Its extreme cold temperature makes it unsafe to consume because the human body is unable to cope with such a cold internal temperature.