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 sites and blowing up natural gas pipelines and threatened 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 not harmed in the attack had been expected to return to Korea on Tuesday, but they're 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 are scheduled to arrive home on Wednesday afternoon.
Another group of 15 Koreans, who were all injured in Sunday's bombing, are expected to depart for Korea on Friday.
Some of them will need additional medical operations.
As for the three Koreans who were killed, the process of returning their bodies is ongoing.
Kwon Soa, Arirang News.