Egyptian investigators say they've found traces of explosives on human remains from the doomed EgyptAir flight that plunged into the Mediterranean in May, killing all 66 people on board.

The cause of the crash has been a mystery, and no group has claimed responsibility for bringing down the plane. The pilot also never issued a distress call, as The Two-Way reported.

Immediately after the crash, Egyptian officials said terrorism was more likely to blame than a technical issue.

Now, Egypt has referred the case to the country's public prosecutor to open a criminal investigation, as Egypt's Civil Aviation Ministry said in a statement. It offered no further details about the type and quantity of explosives detected.

EgyptAir Flight 804 departed from Paris' Charles de Gaulle Airport in the evening on May 19 and disappeared from radar at 37,000 feet over the Mediterranean.

The next month, investigators were able to recover both flight data recorders. They said one of the recorders indicated that there was smoke on the plane before it went down, as we reported.

That was consistent with automated electronic messages from the plane that showed smoke detectors were going off in a toilet and in a section below the cockpit.

Investigators also said in July that the memory chips from the doomed plane's cockpit voice recorder were intact.

France opened a manslaughter inquiry into the crash in June, as we reported.

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