There was this report last year. According to the Russia Times it was revealed as a hoax (hacked twitter account):
http://rt.com/news/egypt-destroy-pyramids-islamists-007/
However, you’ll notice that the supposed tweet came from a Salafi cleric. The Salafist movement is Wahabbi in nature within the Sunni branch of Islam. MB is Sunni. So I’m thinking that the Egyptian Army does not want this virulent strain of Salafism leading the country.