Several people at the scene reported a strong smell of jet fuel.
Children from Park Avenue Elementary School in Cudahy are said to have been exposed.
The fire service had earlier tweeted: "Units on-scene elementary school assessing multiple patients after apparent fuel dump by aircraft on final approach to LAX hits playground."
A Delta spokesman said: "Shortly after takeoff, Flight 89 from LAX to Shanghai experienced an engine issue requiring the aircraft to return to LAX. The aircraft landed safely after an emergency fuel release to reduce landing weight."
Images from the 8000 block of Park Avenue show a huge response from emergency crews Tuesday afternoon.
The incident was reported shortly before 12:30 p.m local time and 70 firefighters and paramedics responded.
The fire service tweeted: "70 firefighters and paramedics on-scene and committed to providing care for those injured. FFs working to confirm substance dropped by aircraft, although initial reports stated smell of jet fuel in area.'
One Twitter user commented: "Now The Whole City Smells Like Fuel And Everything Is Covered In Jet Fuel!"
Another added: "@LAFD is responding to a hazmat, it sounds like people, possible kids at a school, got jet fuel dumped on them from the Delta flight that made the emergency landing."
Two classes are said to have been outside when the jet fuel fell. Students and staff were told to stay inside. The plane later landed safely.
