Children evacuate the Park Avenue Elementary school in Cudahy on Tuesday. (Damian Dovarganes/AP)

Updated Wednesday, Jan. 15 at 2 p.m.

Federal officials are investigating the circumstances that led an airplane making an emergency landing at LAX to dump jet fuel over a populated area. The fuel dump, which appeared to occur at a low altitude, left more than 60 people, including school children, with minor injuries.

Delta Airlines Flight 89 was bound for Shanghai when it had to turn back due to mechanical issues. Federal Aviation Administration officials said on Wednesday that a review of communications with air traffic controllers found the airline crew "did not tell air traffic control that they needed to dump fuel."

The FAA said "air crews will typically notify air traffic control of an emergency and indicate they need to dump fuel. Air traffic controllers will then direct the plane to the appropriate fuel-dumping area."

Our friends at the L.A. Times took a graphical look at what happened on Tuesday:

Our very own @stiles and @LoElebee flipped a quick altitude analysis on yesterday's fuel dump on an LA school.https://t.co/ssmcrjtnhO pic.twitter.com/rrGsN3cKlF — Ben Welsh (@palewire) January 15, 2020

A nearby resident apparently caught the dump on video:

THE CONTEXT

Airplanes often take off with extra fuel that would put them over the maximum weight allowed for a safe landing, according to a recent explainer from USA Today.

In rare cases in which not enough fuel has been consumed before landing, they can release excess to lower the plane's weight. Normally this is done at high enough altitudes that the fuel vaporizes.

Here's a video from another 777 dumping fuel, in which you can see twin jets of fuel spraying from outlets on the outer edges of the two wings.

ON THE GROUND

Word spread quickly on Tuesday that jet fuel had landed on the playground at Park Avenue Elementary School in Cudahy. In all, 20 children and 11 adults who were outside at the time reported minor injuries.

By the end of the day, it was clear the fuel dump covered a wider area east of the airport.

In addition to the 31 patients at Park Avenue Elementary, L.A. County Fire and L.A. City Fire officials said they treated:

Six people at Tweedy Elementary in South Gate

One person at Graham Elementary in the Florence-Firestone area

Six people at San Gabriel Elementary in South Gate

16 people at Jordan High School & 93rd Street Elementary in South L.A.

In addition, at a news conference Tuesday night Downey Fire Department officials said they treated seven children and adults, some at a preschool, some at a home.

Authorities said they used soap and water to treat patients on the scene and no one was taken to a hospital. But parents of affected students said they have questions.

"Why choose a small city, a residential area to dump those fuels? That's not OK," said Nadine Escobar, whose 10-year-old daughter attends Park Avenue Elementary.

Escobar was also critical of school officials for not immediately communicating what had happened. She said her daughter seems fine, but is complaining of itching and she wonders who will take responsibility if other health issues arise.

Cudahy Mayor Elizabeth Alcantor said LAUSD was cleaning school grounds and L.A. County Fire Battalion Chief Jason Robertson said all LAUSD schools will be open Wednesday.

THE TIMELINE

According to the FAA, Delta Air Lines Flight 89 declared an emergency shortly after departing from LAX en route to Shanghai.

LAX officials said the flight was experiencing mechanical issues when it turned back. The plane, a Boeing 777, made an emergency landing at 11:57 a.m. It's scheduled departure time on Tuesday was listed at 11:19 a.m.

Delta Airlines officials said in a statement: "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."

HOW WE REPORTED ON THIS

Reporter Robert Garrova was on site at Park Avenue Elementary. Reporter Elly Yu made calls from the Pasadena newsroom. Brian Frank and Jessica Ogilvie updated this post from our newsroom and news producers Megan Erwin and Lita Martinez provided additional reporting. Editing by Megan Garvey.

LEARN MORE

This story was updated as new information became available.