At least 41 Jordanians have died due to heatstroke during the Muslim Hajj pilgrimage in Saudi Arabia, Jordan said on Tuesday, as temperatures soared in recent days.

The ministry is following the procedures for burying Jordanian pilgrims in Mecca who died due to a heatstroke and continues search operations for missing pilgrims, it said in a statement.

On Monday, Saudi authorities issued warnings to pilgrims to avoid the sun and urged them to postpone the rituals till after 4 pm (1300 GMT).

Islam’s holiest city recorded 51.8 degrees Celsius on Monday, while other nearby holy sites recorded 48 degrees.

Some 1.8 pilgrims took part in this year’s Hajj, one of the five pillars of Islam, which began in Mecca on Friday evening in blistering heat.

Buses and trains are used to help transport the many worshippers to the holy sites, but the large crowds and intense heat still pose a challenge for pilgrims and law enforcement officers.

In recent decades, there have also been several major tragedies with hundreds of deaths due to crowding.