A stampede during the annual Hajj pilgrimage to Islam’s holiest city on Thursday left at least 453 people dead and another 719 injured, Saudi officials said.

The panic and crush were caused by a “sudden rising and overlapping in the density of pilgrims” at a street intersection in Mina, about 3 miles from Mecca, a Saudi Civil Defense spokesman said.

Hundreds of thousands of pilgrims are encamped in tents in Mina, a large valley. From there they process to Jamarat to throw pebbles against three stone walls in a symbolic stoning of the devil.
An estimated two million Muslims from around the world have thronged the holy city to participate in this year’s Hajj, which began Tuesday.

Each year, the Hajj poses a major logistical challenge to Saudi authorities, as crowds of worshipers carry out the prescribed rituals at specific locations in and around Mecca.

Thursday’s disaster was the deadliest at the Hajj since 2006, when more than 346 pilgrims were killed in a stampede in the same area. A panicked charge in a pedestrian tunnel in 1990 left 1,426 people dead. This Hajj season has been tarnished by tragedy. Earlier this month, a crane collapsed at Mecca’s Grand Mosque, killing at least 109 people.