The operator of a drone that crashed onto a triathlete in Geraldton earlier this year has been fined by the Civil Aviation Safety Authority (CASA).

A 20-year-old woman was operating the camera drone above a group of athletes in April when the device unexpectedly experienced radio interference and dropped to the ground.

It crashed onto competitor Raija Ogden, who sustained head injuries.

Last week the Commonwealth Director of Public Prosecutions chose not to proceed with a charge against the operator and handed the matter back to CASA.

The ABC understands CASA has now fined the operator $1,700 for flying the drone within 30 metres of people.

The owner of the drone, Warren Abrams, said he was unaware of any infringement from CASA.

In an earlier statement, the CDPP said the drone crash was not the operator's fault.

"The evidence indicated that the cause of the incident was not the actions of the operator but rather radio interference to the UAV [Unmanned Aerial Vehicle] caused by the event's timing device," the statement said.

However, a spokesman for CASA said there was evidence the drone was flown too close to people.