Screenshot/FlightRadar24

The Los Angeles County Fire Department said in a tweet that 44 people were treated at the scene with minor injuries related to the accident and were released.The fire department said that 20 children and 11 adults were treated at Park Avenue Elementary School in Cudahy, California, while 13 other patients from schools in nearby South Gate and Florence Graham were also evaluated.

The department’s Health HazMat units responded and confirmed the substance was jet fuel.

ABC 7 Los Angeles reported that the victims were complaining of skin irritation.

Two classes were outside in the school’s playground when the liquid “rained down” just before noon, the Los Angeles Times reported.

It was not immediately clear which flight dumped the fuel or why the liquid was discharged. Jettisoning fuel to reduce weight is a common practice when a jet is forced to return to the airport after takeoff, often because of a technical issue or passenger medical emergency.

Typically, jet fuel dissipates when it’s jettisoned from a plane. It was not immediately clear why the fuel ended up reaching the ground in this instance. The Federal Aviation Administration has procedures for dumping fuel for planes heading into or out of major airports, including climbing to higher altitudes when possible and avoiding populated areas.

Delta Flight 89 from LAX to Shanghai returned to the airport shortly after taking off at around the same time, according to data from FlightRadar24. The plane, a Boeing 777-200, passed 2,375 feet over the Cudahy area at 11:53 a.m.

A Twitter user posted video of a plane and said it was the Shanghai flight dumping fuel on approach, but the footage could not be independently verified by Business Insider.

Delta confirmed in a statement to Business Insider that the flight experienced a problem with one of its engines after taking off and had to return to the airport after reducing its landing weight:

“Shortly after takeoff, Flight 89 from LAX to Shanghai experienced an engine issue requiring the aircraft to return quickly to LAX. The aircraft landed safely after a release of fuel, which was required as part of normal procedure to reach a safe landing weight. We are in touch with Los Angeles World Airports and the LA County Fire Department and share concerns regarding reported minor injuries to adults and children at a school in the area.”

The FAA told Business Insider that it was investigating the incident.