The crew of a Boeing 777 that showered schools outside Los Angeles with jet fuel on Tuesday apparently told controllers they were not going to release the toxic liquid right before they did so, newly released audio suggests.

An audio recording of communications between the LAX airport control tower and the pilots of the Delta flight reveals that air traffic controllers asked the crew twice if they needed to get rid of any excess fuel before making an emergency landing due to an issue with the aircraft's right engine.

At one point in the exchange - which was surprisingly calm given the circumstances - the controller can be heard asking the pilot if he was going back to the airport "immediately" or whether he needed to "hold and burn fuel."

At first, the pilot simply dodged the question, saying that the situation "is not critical" and that he was turning the aircraft back to the airport. As the controller pressed further, he asked one more time: "OK, so you don't need to hold to dump fuel or anything like that?" The pilot responded with a rather definitive 'No.' "NEGATIVE," he said.

The audio was obtained through LiveATC.ne, a site that provides a live feed of Air Traffic Control communications around the world, and was published in full by the Los Angeles Times.

It remains a mystery what transpired in the next 20 minutes that forced the pilot to make an about-face and jettison the fuel over heavily populated areas - home to multiple elementary schools - with the Federal Aviation Administration (FAA) now saying that the Delta Flight 89 failed to notify controllers of the move.

"A review of yesterday's air traffic control communications shows the Delta Flight 89 crew did not tell air traffic control that they needed to dump fuel," the US aviation watchdog said in a statement on Wednesday, noting that the dump "did not occur at an optimal altitude that would have allowed the fuel to atomize properly."

While FAA guidelines do not expressly prohibit dropping fuel at such a low altitude - about 2,300 feet at the time of the incident - air controllers typically direct crews to dump it over water or unpopulated terrain. It's standard practice for pilots to drop fuel at an altitude of over 10,000 feet, which ensures the substance evaporates on its way to the ground.

That the move was not per se illegal, however, will likely come as small comfort to dozens of schoolchildren caught off guard and drenched in the toxic downpour. The incident sowed panic on the ground, and led to about 60 people being treated for skin irritation and breathing issues. Some had to be decontaminated with soap and water.

In a statement on Wednesday, Delta, which argued that the fuel dump "was required as part of normal procedure to reach a safe landing weight," said it had sent "13 cleaning crews" to assist local authorities in cleansing all contaminated areas around the schools.

Filed on Friday by attorney Gloria Allred, the suit alleges that the crew of Delta Flight 89 was negligent in dumping the fuel when and where it did, arguing the toxic substance led teachers and students to become "sick, dizzy and nauseated," producing "a lasting and severe irritation and a lasting and noxious taste and smell."

"A Delta Airlines pilot flying at a relatively low altitude and through clear skies dumped massive amounts of toxic jet fuel onto teachers, the school where they worked, onto the children who were in their care, and onto the neighborhood below the jet airplane," Allred said at a press conference announcing the suit on Friday.

The crew of the Delta flight, which encountered an engine malfunction not long after taking off from LAX airport en route to Shanghai, has come under fire after audio surfaced on Thursday detailing the plane's communications with air traffic control. Asked whether he needed to "hold and burn fuel" before making an emergency landing, the Delta pilot gave a clear "negative." It remains unclear why the pilot decided to dump the fuel after that point.

"Our lawsuit alleges that the Delta pilot notified air traffic control personnel of the need for the aircraft to return to Los Angeles International Airport, but the pilot did not inform air traffic personnel of any need to dump fuel in order to lighten the plane for landing," despite being explicitly asked, Allred said.

The four teachers, who have each requested anonymity in the case, are employees of Park Avenue Elementary in Cudahy, a suburb of Los Angeles.

While none required emergency treatment, some 60 students and staff members from six different schools were injured in the bizarre mishap last Tuesday, with one of the Park Avenue teachers suffering "recurring symptoms" after the incident.

I thought, 'Oh my God, it must be a terrorist attack.' All I could do was think of making sure my students were safe and calm... because they were screaming and crying.

The revelations are the latest details to emerge to stoke tensions between the US and its hydrocarbon-rich Gulf ally, in the wake of a Saudi officer's fatal shooting of three Americans at a naval base in Florida last month.

• 4 dead in shooting incident at Pensacola naval base; suspect was Saudi national, officials say - UPDATES
• Nearly 175 Saudi aviation students grounded after Pensacola base shooting

• Is Soros-linked Avaaz group a credible source on fake news? Mainstream media seems to think so
• Avaaz: 'Progressive heroes' or Soros-sponsored librul mob?
• Avaaz: Western imperialist propaganda mill masquerading as grassroots activism
• 'Humanitarian' propaganda war against Syria - Led by Avaaz and The White Helmets

• 38 arrested in Rotherham, UK, as police probe child sex abuse and exploitation on claims of 13 victims
• Telford, UK: 18-month investigation reveals massive child grooming ring; hundreds of girls sold for sex
• On-going nightmare in Rotherham UK: About 1,400 children were 'sexually exploited over 16-year period'
• Investigating Britain's 'sex gangs'
• The prolific sex trafficking in Telford, UK and the left's politically correct ignoring of it
• Oxford, UK: Another Asian 'grooming gang' uncovered; 7 men arrested on multiple counts of rape

• The Amesbury poisoning mystery - magical, morphing 'novichuk'
• Skripal update: English coroner runs out of legal camo, evidence, for postponing Dawn Sturgess death inquest - attempts lying to press
• Coroner in Skripal-Sturgess case forced to announce new inquest hearing under threat of breaking law and lying to press
• A Tale of two Novichoks: UK police unable to say if 'Amesbury nerve agent' is same as 'Salisbury nerve agent'