Rodriguez said the 19-year-old teacher told him she lost control of the vehicle after one of the children pulled on the wheel. The car had only five seats, so some of the children likely traveled without safety belts, he said.
"The teacher had organized a meal in her house," Rodriguez said in a phone interview. "The children were euphoric -- they were very happy to be in the car going to their teacher's house for lunch."
There was no guardrail between the road and the canal, officials said.
Rodriguez said the teacher was thrown from the car and swam to safety. She suffered only minor injuries but was distraught and taken to the hospital for psychological treatment after being questioned by authorities.
Police still were investigating the case, he said.