Updated at 6:43 p.m. ET

Teams treated children and adults for minor injuries at four suburban Los Angeles elementary schools Tuesday after a Delta flight dumped jet fuel on the way to an emergency landing.

The Los Angeles County Fire Department said 20 children and 11 adults were treated for minor injuries when the fuel fell on the playground of Park Avenue Elementary in Cudahy. First responders also treated six people at Tweedy Elementary and six at San Gabriel Elementary in South Gate, along with one at Graham Elementary in Florence-Graham.

No patients were taken to the hospital.

The Federal Aviation Administration said in a statement that Delta Flight 89 declared an emergency after departing Los Angeles International Airport, returned to the airport and landed without incident.

The FAA said it is investigating the incident and that when fuel is dumped, it is supposed to be over "designated unpopulated areas."

The LA Unified School District said students and staff complained of skin irritation or breathing difficulties.

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