Investigators searching for the Air France plane that disappeared over the Atlantic Ocean in June are still searching for answers and require more money and resources to search for the aircraft’s flight data recorder.

Paul-Louis Arslanian, head of France’s Bureau of Investigation and Analysis (BEA) said “At the moment, we can’t explain the accident”.

He said that a further search for the plane and debris in order to locate the flight recorders could cost tens of millions of euros.

“We are making progress and will make progress and I’m optimistic, but this will take time,” he told journalists in Paris. “It takes a year and a half, being responsible and reasonable, in order to make progress and ensure that we’ve run through all of the questions.”

Investigators still cannot pinpoint the location of the Airbus A330 that was enroute from Rio De Janeiro to Paris when it disappeared from radar screens into the ocean, killing all on board.

So far, the search has failed to locate the aircraft’s data recorders, which could mean the cause of the crash may never be fully known.

Arslanian said Airbus has offered to help fund the investigation but more commitments are needed.

“We have to mobilize resources. It’s not only having promises for money, we need to know who will contribute financially and how,” he said.

The aircraft went down more than 900 miles off the coast of Brazil and hit the ocean belly first at a high speed.