Gamal and Alaa are reported to be on the way to Tora prison in Cairo from the Red Sea resort of Sharm el-Sheikh were they were interrogated. They are accused of incitement to fire at demonstrators during a popular uprising earlier this year in which nearly 800 people died. The public prosecutor Abdel Magid Mahmud ordered the inquiry on Sunday as part of a sweeping probe into corruption and abuse.
Prosecutors began questioning the former president and his son Gamal early on Tuesday before state media reported that Mubarak had suffered a heart attack and had been admitted to hospital. According to media reports, Mubarak had refused to eat or drink since he received news on Tuesday morning that he was to be questioned.
The prosecutor's summons came after the release of an audio tape on the pan-Arab television station Al-Arabiya in which Mubarak defended his reputation and complained he was the victim of a smear campaign.
Weekly protests demanding his trial have attracted ten of thousands of people and eventually led to a deadly clash with soliders early Saturday after they tried to clear an overnight demonstration in Cairo's Tahrir Square.