Qantas passengers have told of their fear after they were forced to evacuate their Airbus A330 down slides when the cabin began to fill with smoke.

The Australian Transport Safety Bureau is investigating the incident, in which the flight – which was bound for Perth from Sydney – turned back early on Sunday due to a hydraulic fluid leak.

Passengers told the ABC the plane was stuck on the tarmac after landing when what appeared to be smoke began to fill the cabin.

“We were on the runway waiting to be towed in and we started to smell burning,” Dillon Parker, who is holidaying in Australia from Scotland, said.

One passenger described the incident on Twitter as “terrifying”.

“Just had to evacuate my flight to Perth after engineering issues. Everyone had to exit the plane via slide onto Sydney tarmac after the cabin filled with smoke and the captain screamed evacuate,” Ally Kemp tweeted.

Just had to evacuate my flight to Perth after engineering issues. Everyone had to exit the plane via slide onto Sydney tarmac after the cabin filled with smoke and the captain screamed evacuate. Terrifying.

— Alexandra (@politic_ally) December 14, 2019

Qantas said passengers on the Sydney-to-Perth flight had experienced the “very unusual and probably alarming experience” after flight 575 returned to Sydney about 20 minutes after takeoff at 8.45am on Sunday.

About 20 minutes into the flight, its captain received an alert for one of three hydraulic systems on the aircraft.

“The captain elected to return to Sydney and the aircraft landed safely shortly afterwards. No emergency was declared,” the airline said.

“Once the aircraft was back on the gate there were reports of a thick haze in the cabin, likely caused by hydraulic fluid entering the air conditioning unit.

“While customers may have thought it was smoke, there was no fire.”

Passengers evacuated #Qantas #QF575 A330. The aircraft’s cabin filled with thick haze and smoke and had to return back to to #Sydney.
More: https://t.co/gqcqFM4mHn

📷Dillon Parker#flightmodeblog #flightmode #aviation #avgeek #avgeeks #flights #travel #Traveler #Airbus #Perth pic.twitter.com/zkhGBtoOty

— FlightMode (@FlightModeblog) December 15, 2019

The captain ordered an evacuation of the aircraft and passengers exited by emergency slides and the aerobridge into the terminal, Qantas said.

“Two passengers were treated for injuries sustained from using the slides and another passenger was taken to hospital as a precaution. Some customers reported sore eyes and itchy throats.”

Some passengers told the ABC they had injured their arms or legs as they were pushed by other panicking passengers in the dash for the exit.

Others slammed their heads against overhead luggage compartments as they jumped out of their seats.

Qantas Fleet safety captain Debbie Slade said the airline understood the incident would have been a “very unusual and probably alarming experience for our customers”.

“We thank them for giving crew their full cooperation,” Ms Slade said in a statement.

“The crew did a great job of putting their training into action and following the procedures for a set of circumstances like this.

“We’ll investigate exactly what happened, including liaising with Airbus, before this aircraft is returned to service.”

The airline said it would assist the ATSB with its investigation.

“Qantas is providing support to customers on the affected flight and managing some delays to other flights that occurred as a result of this incident,” the airline said.

“The airline extends its thanks to all customers for their patience and understanding.”

-with AAP