The preliminary report by the Dutch Safety Board on the crash of MH 17 points towards external cause. There was no evidence of technical faults.
The exact wording of the Safety report reads:
Flight MH17 with a Boeing 777-200 operated by Malaysia Airlines broke up in the air probably as the result of structural damage caused by a large number of high-energy objects that penetrated the aircraft from outside. This is mentioned in the preliminary report on the investigation into the crash of MH17 that has been published today by the Dutch Safety Board. There are no indications that the MH17 crash was caused by a technical fault or by actions of the crew.
The cockpit voice recorder, the flight data recorder and data from air traffic control all suggest that flight MH17 proceeded as normal until 13:20:03 (UTC), after which it ended abruptly. A full listening of the communications among the crew members in the cockpit recorded on the cockpit voice recorder revealed no signs of any technical faults or an emergency situation. Neither were any warning tones heard in the cockpit that might have pointed to technical problems. The flight data recorder registered no aircraft system warnings, and aircraft engine parameters were consistent with normal operation during the flight. The radio communications with Ukrainian air traffic control confirm that no emergency call was made by the cockpit crew. The final calls by Ukrainian air traffic control made between 13.20:00 and 13.22:02 (UTC) remained unanswered.
The pattern of wreckage on the ground suggests that the aircraft split into pieces during flight (an in-flight break up). Based on the available maintenance history the airplane was airworthy when it took off from Amsterdam and there were no known technical problems. The aircraft was manned by a qualified and experienced crew.