HONG KONG — The Malaysian government declared on Thursday that the loss of Malaysia Airlines Flight 370 last March was an accident according to the terms of an international air agreement and that the 239 passengers and crew members aboard the plane were presumed dead.

While Malaysian officials had said last spring that the plane appeared to have been lost with all aboard, the step on Thursday cleared the way for death certificates to be issued for the passengers and crew members. It also makes it quicker and easier for Malaysia Airlines and its insurers to pay compensation to the next of kin — although litigation over the amount could continue for years.

But the official declaration did nothing to clear up the mystery of what happened to the plane. The Australian government, which is coordinating a search by four vessels of the sea floor in the southern Indian Ocean, said that efforts to find debris from the crash would continue.

“Australia, Malaysia and China remain committed to the search,” the Australian government said in a statement. “We remain cautiously optimistic the aircraft will be found.”