Norway's Civil Aviation Authority has extended its ban on the use of Airbus H225 Super Puma Helicopters in Norway to include search and rescue missions, the agency said in a statement June 2.

The ban, which also includes an older version of the aircraft, follows the discovery of metal fatigue in the gear box of a Super Puma helicopter that crashed in Norway on April 29, killing all 13 people on board.

The Super Pumas, a workhorse of the oil industry, were banned from commercial traffic in Norway and Britain following the accident, but search and rescue missions had still been allowed.

The findings were published in a preliminary report by Accident Investigation Board Norway (AIBN) on June 1, in which the board urged the European Aviation Safety Agency (EASA) to take immediate action to ensure the safety of the helicopter's main gearbox.

EASA said it was planning to issue another safety directive on June 2, but did not elaborate.

Norwegian oil major Statoil said in a separate statement it would find other ways of operating its emergency services for the Oseberg Field Centre and Statfjord B platforms in the North Sea, as well as at the airport at Sola.

"Statoil is currently mobilizing the necessary resources to safeguard preparedness requirements," the company said.

The helicopter that crashed in April was working for the Norwegian firm and operated by Canada-based CHC Helicopter.

CHC said it welcomed the latest report from the AIBN and that it had suspended all flights with the H225 model as a result, even before the Norwegian ban was announced.

Airbus Helicopters declined to comment further as the investigation continues, a spokesman said on Thursday.

Investigators have ruled out human error, saying the crash was caused by a technical fault.

On June 1, the AIBN said it had found metallurgical evidence "strongly consistent with fatigue" in a part of the gearbox, while adding it was focusing simultaneously on several different scenarios for the crash.

Previous Super Puma incidents linked to gearbox problems included a 2009 crash off Peterhead, Scotland, in which the rotor also flew off and 16 people died.

Airbus Helicopters told operators in a bulletin this week that there were "significant elements" differing from the 2009 crash, according to a copy seen by Reuters.

It placed most emphasis on a possible failure of one of the struts holding the rotors to the aircraft, saying that could have been caused by either faulty bolts or missing safety pins.

Design and production are the responsibility of Airbus Helicopters; maintenance is handled by CHC.