Three-hundred and twenty-eight days after it first went missing with 239 passengers and crew on board, Malaysian investigators on Thursday formally declared the disappearance of Flight MH370 an accident.

The declaration by Malaysia’s Civil Aviation Authority clears the way for families to pursue compensation claims.

Investigators concluded that the aircraft exhausted its fuel supply over the southern Indian Ocean, and is on the sea floor. Everyone on board the flight was declared dead. An underwater search west of Perth, Australia, is still taking place.

“It is with the heaviest heart and deepest sorrow that we officially declare Malaysia Airlines Flight MH370 an accident,” Azharuddin Abdul Rahman, the director general of Malaysia’s civil aviation department, said in a statement.

He said that the “declaration is by no means an end” and that the search for the jet remains a priority. “At this juncture, there is no evidence to substantiate any speculations as to the cause of the accident,” he said.

The plane disappeared on March 8 last year en route from Kuala Lumpur to Beijing. It is presumed to have crashed in the southern Indian Ocean off the coast of western Australia.

Azharuddin described the search and rescue mission in the South China Sea, the Straits of Malacca, the Andaman Sea and the southern Indian Ocean as an “unprecedented exercise” which involved aircraft and vessels from 13 countries. It was called off late April and became a search and recovery phase.

He said Malaysia, China and Australia had spared no expense and resources in the search for the plane, which has covered more than 5,300 square miles. The hunt resumed in October after a four-month hiatus with more sophisticated sonar equipment.

Azharuddin said search teams had pursued every credible lead and reviewed all available data, but were yet to find the missing aircraft.

He said that Chapter 1 of Annex 13 to the Convention on International Civil Aviation, commonly referred to as the “Chicago Convention,” said the definition of the term “accident” includes “the aircraft is missing”.

“It also states that “an aircraft is considered to be missing when the official search has been terminated and the wreckage has not been located,” Azharuddin added.