According to the source, the court had postponed trial proceedings in order to hear witness testimonies and review "evidence" said to be stored on CDs.
The court has already imposed a media blackout on the trial, Turkey's Anadolu Agency reported.
Defendants face charges of "conspiring" with Palestinian resistance group Hamas and Lebanon's Hezbollah to carry out "terrorist acts" inside Egypt.
Mursi and his co-defendants emphatically deny the charges against them, which they insist are politically driven.
Mursi, Egypt's first democratically elected leader, was ousted by the military last July – after only one year in office – following protests against his presidency.
He currently faces multiple criminal charges, including incitement to murder, jailbreak and "offending Egypt's judiciary."