A Delta airlines plane bound for Shanghai had to turn back and make an emergency landing at the Los Angeles International Airport Tuesday after facing issues with the engine. The plane dumped fuel to reduce weight as it flew over Park Avenue Elementary School in the city of Cudahy.

Four other schools, including two in South LA were also affected by the jet fuel and treated by L.A. city fire officials.

The L.A. County Fire Department released a tweet soon after stating that firefighters and paramedics were on the scene and assessing injuries. They later provided an update that 31 patients, including 20 children and 11 adults, were evaluated by firefighters and released with minor injuries after denying assistance to the hospital.

Delta airlines officials released a statement saying, “The aircraft landed safely after a release of fuel, which was required as part of normal procedure to reach a safe landing weight. Delta is in touch with Los Angeles World Airports and the LA County Fire Department as well as community leaders, and shares concerns regarding reports of minor injuries to adults and children at schools in the area."

The Federal Aviation Authority said it was investigating the issue and checking if the plane had followed proper dumping techniques.

The FAA wrote in a public statement following the incident that “there are special fuel-dumping procedures for aircraft operating into and out of any major U.S. airport. 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 L.A. Unified School District Board Vice President Jackie Goldberg said in a statement that students and employees on the playground when the jet passed were affected by the fumes and had to be treated for injuries, breathing problems and skin issues.

She also said that educators visited classrooms to ensure the safety of their students and experts from Los Angeles Unified’s Office of Environmental Health and Safety were working to make the campus safe and decontaminated for today.

“My office has been in contact with government officials and Los Angeles Unified staff to ensure the health and safety of all involved,” Goldberg wrote in a statement. “I will continue to advocate for our Park Avenue Elementary School family, and provide updates when more information is available. I am sorry our school community had to go through this very scary incident today.”

CBS LA reported that the flight would resume to Shanghai Wednesday and all LAUSD schools affected by the incident would remain open today.