For full coverage in Arabic, please visit CNN Arabic.

Story highlights

NEW: At least 13 nations confirm pilgrim deaths; Saudi Arabia says six of its civil defense workers injured

The stampede took place in Mina, where worshippers symbolically throw rocks at the devil

Some say timing, heat and pilgrims going in opposite directions may have contributed to the deaths

CNN  — 

A day after a deadly crush killed 717 people during the Hajj in Saudi Arabia, a critical question remained Friday: What caused the chaotic stampede?

Among the suggested causes: pilgrims rushing to complete the rituals, heat, masses of faithful pushing against each other in opposite directions, even confusion among the many first-timers on the annual Islamic pilgrimage to Mecca and Mina.

Too many people, too little time

More than 2 million Muslims from around the world are in Saudi Arabia for the Hajj, a pilgrimage that all Muslims who have the financial and physical ability make at some point in their lives.

The millions of people must perform a litany of rituals in five days, including the symbolic stoning of the devil in Mina, about 2 miles away from the Mecca holy site.

That’s where the deadly stampede took place Thursday, the third day of the five-day event. Officials say 717 people died and 900 were injured.

Iran’s semiofficial FARS news agency said that 131 Iranians were among the dead. Another 365 remained missing, the state-run IRNA news agency reported, cautioning