Airbus has ordered checks on three types of helicopters following a fatal crash in Norway, Norwegian authorities said on Wednesday.

Five Norwegians and their Swedish pilot died when their AS350B3e helicopter crashed in Arctic Norway on Aug. 31. Norwegian investigators have not concluded on the cause.

Following preliminary findings linked to the connection between the engine and the main gearbox, Airbus Helicopters has issued an emergency alert service bulletin (EASB) calling for visual inspections of this area on all recently delivered AS350, AS550, and EC130 helicopters, investigators said.

"According to Airbus Helicopters, issuance of the EASB (notice) is a precautionary measure to ensure the continued airworthiness of the helicopter type," the Accident Investigation Board Norway said in a statement.

The crashed aircraft had flown just 73 hours, it added.

Airbus was not available for immediate comment.

Helitrans, the operator of the crashed helicopter, said it had performed the prescribed inspections on its 15 remaining helicopters of the same type.

"There were no discoveries of any kind. In accordance with the recommendations from Airbus, the helicopters are thus cleared to fly and will be put back into operation," the company said in a statement.

In 2016 an Airbus Super Puma helicopter crashed off the coast of Norway, killing all 13 people aboard, the result of metal fatigue in its gearbox.

As a result, Norwegian authorities recommended Airbus revise the design of the main gearbox of its AS 332 L2 and EC 225 LP Super Puma helicopters. These models are different from the model that crashed in August.

In the 2016 crash, the Super Puma's main rotor blades separated from the helicopter as it was ferrying passengers from an offshore oil platform.