Investigators are searching for a missing piece of the engine of the SA Airlink plane which crashed last month, the Civil Aviation Authority (CAA) said on Thursday.

"It is not known at what stage of flight this part may have separated from the engine. It is possible that someone may have inadvertently removed it from the wreckage site," the CAA said in a statement.

"Notwithstanding, recovery thereof would certainly assist in facilitating the investigation process."

The part, about the length of a cooldrink can, is a metal disk with a rod joined to its centre.

The SA Airlink flight floundered and tried to land on a school sports field in Merebank, three kilometres from Durban International Airport, shortly after take-off on 24 September.

The pilot, two flight attendants and a cleaner on the ground were injured. Pilot Allister Freeman died in hospital on Wednesday.