The residents of Chilapa in Guerrero state were hospitalised after the rally held earlier this week by the Institutional Revolutionary Party. Their condition has now improved.
The people were invited to a rally with promises of gifts and food, other participants said.
After going home, the victims experienced vomiting, dizziness and diarrhoea.
Some people said at least 70 children were also sickened by the food, but health officials did not confirm the figure.