(CNN) -- Dozens of Mexican schoolchildren were hospitalized after apparently falling ill from a meal at their kindergarten.
At least 38 children ages four and five became sick after lunch at a state-run school in San Luis Rio Colorado, which sits right on the border across from Yuma, Arizona, emergency dispatcher Carlos Ibarra said.
A local clinic alerted emergency officials Friday when 15 children suddenly showed up at their facilities with similar symptoms -- vomiting, diarrhea and fever, Ibarra said.
The number more than doubled before the day was over.
The children had eaten chicken salad and homemade agua de horchata. a refreshing rice water drink. Officials suspect the horchata was responsible for the food poisoning, Ibarra said.
Some of the children were released from the hospital on Friday night.
The food was prepared by the sister of one of the teachers who had been contracted by the school, Ibarra said.
The school, named Manuel Cervantes Imaz, has a total of 312 students.
The health department will conduct an investigation, he said.