What’s behind deaths at this year’s Hajj pilgrimage in Saudi Arabia?

Hundreds of people are thought to have died during the Hajj pilgrimage in Saudi Arabia – most of them due to extreme heat as temperatures soared past 51 degrees Celsius.

AFP news agency quoted an Arab diplomat as saying 658 Egyptians had died. Indonesia said that more than 200 of its nationals had died. India said 98 people were known to have died.

Pakistan, Malaysia, Jordan, Iran, Senegal, Tunisia, Sudan and Iraq’s autonomous Kurdistan region have also confirmed deaths. The US believes a number of Americans died, the Wall Street Journal reported. Friends and relatives have been searching for those missing in hospitals and posting messages online.

Hajj is the annual pilgrimage made by Muslims to the holy city of Mecca. All Muslims who are financially and physically able must complete the pilgrimage at least once in their lifetime. About 1.8 million people have taken part this year, Saudi Arabia says.

More than half of those who died were unregistered pilgrims and joined the Hajj through irregular channels, leaving them unable to access cooling facilities such as air conditioned tents and buses, AFP reports.

On Friday Jordan said it had detained several travel agents who facilitated the unofficial travel of Muslim pilgrims to Mecca. Egypt is conducting a similar investigation.

Saudi Arabia has increased safety measures at the Hajj in recent years, but it still faces criticism for not doing enough, particularly for unregistered pilgrims. It has not yet commented on the deaths.

Here are some of the factors contributing to the deaths.