More than 700 pilgrims were killed on Thursday from a stampede during the annual Muslim Hajj pilgrimage in Saudi Arabia, and the death toll continues to rise.

Almost 900 people were injured in the incident at Mina, on the outskirts of the holy city of Mecca. The tragic incident occurred as two million pilgrims took part in the Hajj's last major rite.

It is the deadliest incident to occur during the pilgrimage in the last 25 years.

Mina is where pilgrims carry out a symbolic stoning of the devil by throwing pebbles against three stone walls. The pillars stand where Satan is believed to have tempted the Prophet Abraham.

It also houses more than 160,000 tents where pilgrims spend the night during the pilgrimage.

Saudi Arabia's crown prince, Prince Mohamed bin Nayef, ordered a probe into how the tragedy occured.

Nayef, who chairs the Saudi hajj committee, ordered the investigation during a meeting with senior officials responsible for the pilgrimage in Mina.

Saudi King Salman bin Abdulaziz Al Saud later ordered an urgent review of this year's Hajj plans to improve the level of organization.

"Regardless of the investigation results, the improvement of the methods and mechanisms of the Hajj season will not stop. We have instructed the concerned entities to re-evaluate the current policy and the distribution of responsibilities," he said.

Saudi Arabian Ministry of Interior Spokesman, Mansour Turki, points out that the investigation will look into what caused an unusual density of pilgrims to congregate at the location of the disaster. "The reason for that is not known yet," he said at a news conference in Mina.

The Health Minister Khalid al-Falih said that the stampede was "possibly caused by the movement of some pilgrims who didn't follow the guidelines and instructions issued by the responsible authorities".
It is the second disaster to strike Mecca in two weeks, after a crane collapsed at the Grand Mosque, killing 109 people.