A mist of fuel dumped by an airliner with an engine problem as it made an emergency return to Los Angeles International Airport fell on several schools Tuesday, causing minor skin and lung irritation to 56 children and adults, officials said. The fuel sprayed out of the plane in two lines and the strong-smelling vapour descended at midday in the city of Cudahy and nearby parts of Los Angeles County, about 13 miles (21 kilometres) east of the airport.

The vapour fell on five elementary schools, but all injuries were minor and no one was taken to hospitals, Los Angeles County Fire Department Inspector Sky Cornell said. It didn’t force any evacuations.

“That’s a great sign,” Cornell said.

All the fuel evaporated very quickly and nothing flammable remained in the air or on the ground, he said.

People were treated with soap and water, Fire Inspector Henry Narvaez said.

Shortly after takeoff, Delta Air Lines Flight 89 to Shanghai “experienced an engine issue requiring the aircraft to return quickly to LAX. The aircraft landed safely after release of fuel, which was required as part of normal procedure to reach a safe landing weight,” the company said in a statement. The airline did not release details about the engine problem.

The Federal Aviation Administration said it is investigating.

“There are special fuel-dumping procedures for aircraft operating into and out of any major US 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.”

The FlightAware website’s flight track showed the jet took off over the ocean and made an immediate right turn toward land and circled back over Southern California to approach the airport from the east.

Delta said it was in touch with the airport and Fire Department and shared “concerns regarding reported minor injuries to adults and children.”

The Los Angeles Unified School District said its Park Avenue Elementary campus in Cudahy and 93rd Street Elementary had “direct impacts from the fuel.”

Cornell said 31 children and adults were affected at Park Avenue, and 12 at 93rd Street. The rest of those affected were at other schools.

The school district said in a statement that paramedics were immediately called to treat anyone complaining of “skin irritation or breathing problems” and that its environmental health and safety office also responded.

Some teachers at Park Avenue had headaches from the smell, said Antonio Buenabad, area representative for the United Teachers Los Angeles union.

“They were anxious to get home and shower because the stench was very strong,” he said of the teachers.

A high school was also affected, but no one was treated there.