Four teachers are suing Delta Air Lines after one of its aircraft dumped fuel over schools as it made an emergency landing.

The flight was forced to return to Los Angeles International Airport because of engine problems.

Delta confirmed the plane had dumped the fuel to reduce its landing weight. Nearly 60 people were treated at six local schools, many of them children.

The four teachers are now seeking unspecified damages over the incident.

"The plaintiffs could feel the fuel on their clothes, their flesh, their eyes and their skin," a lawyer for the teachers said, adding that the fuel "penetrated their mouths and noses as well, producing a lasting and severe irritation".

The teachers filed the suit in Los Angeles Superior Court on Friday. According to the Los Angeles Times, the suit says jet fuel is dangerous to humans and cites the US Agency for Toxic Substances and Disease Registry.

Delta has yet to comment on the lawsuit.

The flight was bound for Shanghai. It landed safely shortly after the fuel dump, with all 167 passengers and crew unharmed.

Delta has already been cited by the South Coast Air Quality Management District for a violation. The agency characterised the fuel dump as a public nuisance.

It comes after the Federal Aviation Administration (FAA) launched an investigation into the incident immediately after Tuesday's emergency landing.

Aviation rules say that planes can dump fuel in emergency landings, but only over designated areas and at a high altitude.

On Wednesday, the FAA said the crew had released the fuel without telling air traffic control.

A transcript of radio transmissions made public after the incident revealed that the pilot had initially told controllers there was no need to dump, before later releasing the fuel.