I'm sorry to say that when things are going badly, the Egyptian media, especially the more sensational newspapers (state-run and private) and the often irresponsible TV talk-show hosts, start looking for conspiracies. Israel, the US, the Muslim Brotherhood, Iran, and he Freemasons are the usual suspects, often in improbable combinations (Iran and the US together; Israel and the Muslim Brotherhood).
While most of the rest of the world is convinced the plane was brought down by a bomb, and even the Egyptian investigators do not rule that out, the media is seeing an international conspiracy to subvert Egypt. Al-Watan on Sunday had a banner headline, "Egypt Defies Terrorism of the West." (Link is to the story in Arabic.) I would note that the most draconian step so far was Russia's decision to cancel all flights to Egypt, and Russia is usually not considered "the West," but never mind.
There remains a possibility it was not a bomb. But the media, including the state media (perhaps with government sanction) is reacting in a prickly, defensive way that could make things worse if indeed it was a bomb. (Conversely, the US and Britain could look very bad if it wasn't.)