Norway chopper crash
Rescuers work at a site where a helicopter crashed, west of the Norwegian city of Bergen, April 29, 2016. NTB Scanpix/Bergens Tidende/via REUTERS

Norway’s Civil Aviation Authority extended the ban on Airbus H225 Super Puma helicopters to its use in search and rescue operations, the agency announced Thursday. The ban comes after investigators found metal fatigue in the gearbox of a Super Puma helicopter that crashed in the southwestern Norwegian city of Bergen in April, killing 13 people.

After the accident, Norway and Britain had banned the Super Puma helicopters from commercial use. The initial ban had exempted the helicopters for search and rescue operations.

Norwegian oil giant Statoil issued a separate statement Thursday saying it has decided to suspend the use of H225 helicopters. The company uses H225 — earlier known as EC225 — for emergency services for the Oseberg Field Centre and Statfjord B oil field in the North Sea and also at the airport in the western city of Sola city.

“As the responsible party for preparedness in these areas, Statoil is obliged to ensure preparedness in compliance with applicable regulations. Statoil is currently mobilizing the necessary resources to safeguard preparedness requirements,” the company said.

In the April 29 accident, the Airbus Super Puma helicopter was heading to Bergen from the Gullfaks field in North Sea. The chopper crashed near the small island of Turøy.

Following the incident, the Accident Investigation Board Norway issued a preliminary report saying it had found “features strongly consistent with fatigue” in parts of the main gearbox.

“It cannot be ruled out that this signifies a possible safety issue that can affect other MGBs [main gearbox] of the same type. The nature of the catastrophic failure of the LN-OJF main rotor system indicates that the current means to detect a failure in advance are not effective,” according to the board's findings, cited by the BBC.

Separately, Bristow Group Inc. and CHC Group Ltd., the world’s two largest helicopter operators, suspended all flights that use the H225 models, the Wall Street Journal reported. The April crash had prompted Bristow Group of Houston to suspend most of its H225 choppers, except for search and rescue missions and training flights. CHC Group, the Vancouver operator of the helicopter model that crashed, also said it had stopped all flying with H225.