The suicide bomber who blew up a tourist bus in Taba on Sunday used an explosive belt, a forensics authority spokesperson has announced.
The homemade bomb weighed between five and ten kilograms, Hisham Abdel-Hamid added.
Islamist militant group Ansar Beit Al-Maqdis has said it carried out the attack that killed three South Koreans and an Egyptian.
The group warned it was part of its "economic war" against the Egyptian authorities, which it said were "traitors."
Abdel-Hamid it was a small bomb but the exploding body of the suicide bomber and a woman next to him caused a large echo.
The bomber was aged over 21, according to forensic examinations.
The attack on the bus, which was travelling to Israel from St Catherine's Monastery, a popular tourist destination in South Sinai, was the first assault on tourists since president Mohamed Morsi's ouster in July 2013 spurred an Islamist insurgency.