(CNN) -- Authorities treated more than 700 people for food poisoning after a political rally in southern Mexico this week, officials said.

Exactly what caused the food poisoning was unclear, officials from the healthy ministry in Mexico's Guerrero state said Wednesday. Authorities were testing food and drink samples from the event and sending representatives to communities throughout the area to look for additional cases.

Alberta Garcia Adame told CNN affiliate Televisa she started to feel sick after eating egg tacos at a rally Tuesday in Chilapa, Guerrero, for Sergio Dolores Flores, who is running for congress as a candidate for Mexico's Institutional Revolutionary Party.

As the number of cases grew, doctors treated many patients at a local hospital and a temporary shelter at the back of a local church, Televisa reported.

Guerrero State Health Secretary Rufino Dominguez said in a statement Wednesday that nearly all of the patients had been treated and released.