MOSCOW — The mystery deepened Monday over the weekend crash of a Russian charter plane on the Sinai Peninsula in Egypt that killed all 224 aboard, with company executives ruling out technical or human error only to be upbraided by aviation officials who called such assertions premature.

As representatives from at least five countries joined the investigation of the Airbus jetliner crash, new questions also arose about the aircraft’s repair history and the possibility that a terrorist act felled it on Saturday.

The Metrojet flight full of mostly Russian vacationers, bound for St. Petersburg from the Egyptian resort of Sharm el Sheikh, plummeted after having reached cruising altitude, scattering in chunks and bits across almost eight square miles.

The lack of information has been exacerbated by unsubstantiated claims from the Islamic State that its militants destroyed the aircraft to avenge colleagues killed by Russia’s immersion into the Syria war.