A Delta Air Lines Inc. jet dumped fuel over elementary school playgrounds in Los Angeles, causing skin irritations and breathing problems for 44 children and adults, after an engine problem forced the plane to turn around shortly after takeoff.

The injuries were minor and none of the victims was taken to hospitals, the Los Angeles County Fire Department said in a tweet Tuesday. Students and adults “may have been sprayed by fuel or inhaled fumes,” the Los Angeles Unified School District said in a statement about the health effects.

Firefighters reported victims from at least four schools. The Federal Aviation Administration said it was “thoroughly investigating” the incident.

“There are special fuel-dumping procedures for aircraft operating into and out of any major U.S. airport,” the FAA said in a statement. “These procedures call for fuel to be dumped over designated unpopulated areas, typically at higher altitudes so the fuel atomizes and disperses before it reaches the ground.”

Delta Flight 89, a Boeing Co. 777-200ER, left Los Angeles International shortly after 11 a.m. local time en route to Shanghai. The plane experienced an engine problem shortly after takeoff that required it to return to the airport, Delta said in a statement.

“The aircraft landed safely after an emergency fuel release to reduce landing weight,” the airline said, without providing further details.

The jet climbed to 7,775 feet before it began to descend after less than three minutes in flight, according to Flightradar24, an aircraft tracking service. The entire flight lasted 24 minutes, Flightradar24 data showed.