European aerospace giant Airbus has issued instructions for the immediate inspection of several models of its helicopters following an accident in Norway in which six people were killed.
About 400 aircraft are concerned by the order, which Airbus said should require about one hour per helicopter.
The firm said it had issued on Tuesday "an Alert Service Bulletin (ASB) instructing operators to conduct an inspection of the interface between the engine and the main gear box on all recently delivered H125 (AS350 B3e), AS550 and H130 helicopters."
A crash of a H125 in the far north of Norway near the town of Alta on August 31 killed six people.
"This is a precautionary measure in the light of initial findings by the official investigation," said Airbus Helicopters.
"We would emphasise that it does not imply that the root cause of the accident is known," it added.
Norway's Accident Investigation Board (AIBN) for its part called the bulletin an emergency alert calling for an immediate visual inspection of the area.
"According to Airbus Helicopters, issuance of the (alert) is a precautionary measure to ensure the continued airworthiness of the helicopter type," it said in a statement on Wednesday.
AIBN said the helicopter which crashed had only 73 flight hours and there was no indication the owner had performed any work on the area in question.
The alert was issued following the first detailed examinations of the components of the crashed helicopter on Tuesday, which AIBN said was done in cooperation with its French counterpart BEA as well as Airbus Helicopter and the engine manufacturer, Safran Helicopter Engines.
"The examinations of the accident helicopter is still ongoing," said the AIBN, which also added that no conclusions about the cause of the accident had been made.