At least 57 students from the Juana de Asbaje secondary school in Bochil municipality, were brought to the hospital on October 7 with symptoms of poisoning by an unidentified substance.
According to reports, the symptoms ranged from nausea, and drowsiness to abdominal pain, and fainting. Parents were cited as speculating that the students had ingested contaminated food or water at the cafeteria during a Friday school event.
Footage has been circulated on social media showing the chaotic scene at the local hospital as teenagers in school uniforms were being rushed to receive medical assistance.
After claims by some parents that the students had unknowingly ingested cocaine, the state prosecutor's office said on Saturday that, following toxicology tests, 15 samples came back "negative for prohibited substances, drugs of abuse." However, it added that further testing would be conducted.
Earlier, a video on social media reportedly showed one man saying his daughter had been poisoned and tested positive for cocaine at a private laboratory, along with other students.
The authorities have not made any official statements regarding the cause of the mass poisoning. The prosecutor's office said it was investigating the incident. However, the alarm has been growing as local media have reported two previous cases of poisoning of dozens of students in the city of Tapachula, in the far southeast of the state of Chiapas, since September 23.
MNA/PR