(Updates with Canadian aviation agency comments)
PARIS/TORONTO, Oct 2 (Reuters) - Air accident investigators from both sides of the Atlantic have been struggling to decide who should lead a probe into an engine explosion that forced an Air France A380 to make an emergency landing in Canada, people familiar with the matter said.
Two days after the damaged superjumbo landed at Goose Bay in Labrador with more than 500 people on board, a formal investigation had yet to be announced, a step that typically takes hours.
Experts from the United States and France, as well as planemaker Airbus and U.S-based engine maker Engine Alliance, have been sent to Goose Bay.
But a spokesman for France's BEA air accident agency said no investigation had yet been formally launched.
Canada's Transportation Safety Board (TSB) said it was currently leading the work of investigators from Canada, France and the United States.
"Its a long process and were still gathering data and assessing. Many significant elements remain to be determined at this point," TSB spokesman Alexandre Fournier said by phone from Ottawa.
The decision on who should lead an investigation depends on a number of factors including, first and foremost, the country where the incident took place.
Airline sources said an "uncontained explosion," which ripped off the outer-right engine's three-metre-wide fan together with its housing from the front of the engine, happened over Greenland, which comes under Danish jurisdiction.
Under aviation law, Denmark would officially own the investigation but it can delegate it to another country, such as Canada.
Denmark's accident agency was not available for comment.
France and the United States would automatically be part of any investigation, since the aircraft and engine were made in those countries respectively.
Nobody was injured in the incident, in which Air France Flight 66, originating in Paris and bound for Los Angeles, declared a mayday and diverted to Canada.
Airbus has issued an alert to all operators of the aircraft that use the same type of engine, confirming the low-pressure compressor fan had been separated. No cause had yet been identified, it said, according to one recipient.
In 2010, a Rolls-Royce engine on a Qantas A380 suffered mid-air damage after taking off in Singapore. An investigation blamed a leak from a badly made engine pipe. (Reporting by Tim Hepher in Paris and Anna Mehler Paperny in Toronto; Editing by Jane Merriman and Bill Trott)