Regional airline REX is under investigation by the aviation safety watchdog after reports of uninvestigated corrosion on a plane.

The Daily Telegraph has published footage of the plane’s propeller shaft, which appears to be discoloured and could be rust.

Civil Aviation Safety Authority spokesman Peter Gibson confirmed the regional carrier was under scrutiny.

“CASA will be investigating the video showing possible corrosion on a REX aircraft propeller as part of the overall review of REX maintenance,” he said.

The airline’s deputy chairman John Sharp disputed the report, saying the plane was in Adelaide at the time having a routine check and wasn’t carrying passengers.

“An engine will, over a period of time, get some muck on it. You will, from time to time, get a solvent and you will wipe it off. And that is exactly what has happened,” he told 2GB.

“It is bright and shiny; it’s all been cleaned. It has not been uninvestigated.”

The Civil Aviation Safety Authority conducted a full-day audit at the main REX maintenance base in Wagga Wagga on Thursday.

Investigators looked at hangars, aircraft and repair work, as well as interviewing engineers and reviewing maintenance records.

While the safety authority hasn’t found any immediate concerns, Mr Gibson assured travellers the investigation would continue until questions about safety were fully answered.

“CASA will be seeking further information from REX as questions remain not fully answered,” he said.

“If immediate safety issues are found CASA will take timely and appropriate action.”