The bombing of a tourist bus on Sunday in Taba, South Sinai, was caused by a suicide bomber who boarded the bus and detonated the explosion immediately after, said interior ministry spokesperson Hani Abdel-Latif.
Prior to the blast, the bus driver had accompanied two South Korean tourists to the baggage hold. As they returned to the bus, an unknown man followed them inside and the bomb went off immediately, said Abdel-Latif, as reported by Al-Ahram's Arabic news website.
The bomber took advantage of the moment when the bus door was open and the driver and the two tourists were returning to their seats, Abdel-Latif added.
Sunday's attack on a bus filled with 33 tourists not far from the Israeli border was the worst terrorist attack in the South Sinai resort area in almost eight years.
Abdel-Latif said that according to preliminary investigations, the death of the suicide bomber would bring the death toll to five – three South Koreans, the Egyptian bus driver, plus the bomber. At least 14 others were injured.
The bomber has not yet been identified. Security forces have found body parts at the site of the blast, which likely belong to the bomber, Abdel-Latif said, but investigations are still ongoing.
At the time of the explosion, the bus was being followed by security forces in separate vehicles, protocol for tourist convoys in South Sinai, Abdel-Latif said. One security officer was injured in the blast.
Abdel-Latif blamed the Muslim Brotherhood for the attack.
No group has yet claimed responsibility for the bombing.
Abdel-Latif said that Egypt's Interior Minister Mohamed Ibrahim is implementing a new security plan to further secure all tourists and tourist sites in the country.
Earlier on Monday, health minister Maha El-Rabat and tourism minister Hisham Zaazou travelled to Sharm El-Sheikh International Hospital to visit those injured in the blast.
Egypt has been rocked by a wave of bombings since the ouster of Islamist president Mohamed Morsi in July. Ansar Beit Al-Maqdis, a militant group from Sinai that is affiliated with Al-Qaeda, has claimed most of the attacks, which have largely targeted security installations and personnel.
Sunday's bombing was the first time civilians had been directly targeted.
The last major attack on tourists in Egypt was in April 2006, when a bomb killed 23 people in Dahab in South Sinai.