A defence official said Israel's Defence Ministry had bought 40,000 tents, each with the capacity for 10 to 12 people, to house Palestinians relocated from Rafah in advance of an assault
The suspects, which included foreign and Saudi citizens, were detained in the Western port city of Jeddah, state news agency SPA quoted the interior ministry as saying.
Three suicide bombers and two members of the security forces were killed in the unprecedented attack on the mosque and tomb of Islam's prophet Mohammed that is one of the religion's holiest sites.
There was no claim of responsibility for the attack nor did the interior ministry statement blame a specific group.
Islamic State, based in Iraq and Syria, has carried out a series of bombings and shootings in Saudi Arabia since mid-2014 killing scores of people, mostly members of the Shia Muslim minority and security services.