Egyptian security forces say a suicide bomber was probably behind Sunday's deadly bus bombing in Sinai that killed four people, including three Koreans.
After reviewing CCTV footage of the attack, police concluded a suicide bomber had boarded the tourist bus and detonated his explosives near the door.
A spokesman from Egypt's interior ministry said Monday that the preliminary investigation shows some tourists disembarked to get their bags, when a man walked onto the bus and an explosion followed when he reached the third step.
The bus, carrying mostly Korean tourists, was waiting to cross into Israel at the border when the blast took place.
An al-Qaeda-linked Islamist group Ansar Beit al-Maqdis has claimed responsibility for the bombing, saying it had previously warned it was planning an attack.
In an online statement Monday, the group promised to "continue to target the state's leaders and economy by hitting tourism and exploding the natural gas pipelines," threatening additional attacks in the next few days.
Sunday's bombing was the first targeting tourists since the overthrow of President Mohamed Morsi last July, sparking fears Islamic militants are turning to attack Egypt's tourism industry, which is a pillar of the country's economy.
Meanwhile, 15 survivors, who were expected to return to Korea on Tuesday, are still in Israel as they are struggling to find a flight home.
An official at the Korean embassy said the group is planning to board a flight from Istanbul and added they will arrive in Korea on Wednesday afternoon at the earliest.
Eleven of the 13 injured Koreans have undergone surgery to remove fragments and debris from their bodies.
Two more will stay in Israel a little longer as they need to have further operations.
The bodies of the three dead Koreans have also been transferred to Tel Aviv and are undergoing return procedures.
Hwang Sung-hee, Arirang News.