CAIRO — Traces of explosives have been detected on the bodies of passengers retrieved from EgyptAir Flight 804, which plunged into the Mediterranean Sea in May, killing all 66 people on board, Egyptian officials said Thursday.

The announcement by the Civil Aviation Ministry offers the strongest suggestion yet that a bomb may have felled the airliner as it flew to Cairo from Paris. Previously, officials had focused on a fire as a likely cause.

It was not immediately clear from the announcement when Egyptian officials had drawn this conclusion.

The timing of the announcement came amid new fears in Egypt over intensifying violence by the Islamic State and affiliated groups. Islamic State militants claimed responsibility for a deadly bombing of a Coptic cathedral in Cairo on Sunday and vowed more such attacks.

No militant group has claimed responsibility for the EgyptAir crash, and some experts say there could be other explanations for the explosive traces besides a bomb.

Readings from the plane’s data and voice recorders, released by Egypt during the summer, indicated that smoke had spread through the cockpit just before the crash and that one of the pilots had warned of a fire.

Investigators have said they did not know what caused the blaze, but the evidence indicated that the plane broke up in midair after the fire overwhelmed the crew.

In September, the newspaper Le Figaro reported that French officials had found traces of explosives on the wreckage but that their Egyptian counterparts had prevented them from conducting further tests. Egyptian officials cited in the article denied that the French team had been obstructed.

New York Times