The company that owns the plane that crash-landed into the ocean off Darwin on Friday says it is too early to determine the cause of the accident.

The pilot of the Piper Chieftain says one of the engines failed and he was forced to ditch the plane into the harbour.

All six people on board escaped the crash unharmed, though they were forced to swim ashore.

The plane was hoisted on to a barge late on Saturday and is now in the hands of CSG's insurers.

CSG managing director Denis Mackenzie says other services will not be affected by the incident.

"I think CASA (Civil Aviation Safety Authority) or ATSB (Australian Transport Safety Bureau) will be investigating and we'll find out in a couple of months," he said.

"We will have planes and other equipment going to Maningrida early next week."

Mr Mackenzie says despite the loss of company assets, he is relieved nobody was hurt.

"The loss is inconsequential really. I'd say there would have been computers and things and different equipment on the plane, the main thing is they all got out."

CSG says it will conduct an internal investigation into the crash.