CAIRO (AP) — Every year, millions of Muslims converge on the Saudi holy cities of Mecca and Medina for the annual hajj pilgrimage, with the massive ceremonies representing a major security and logistical challenge for the kingdom’s authorities.

On occasion, the hajj and events surrounding it have been marred by accidents and tragedies, such as Friday’s crane collapse on the Grand Mosque in Mecca that killed 107 people. In the heavy traffic, crushes and pileups have killed hundreds in the past.

Here’s a look at some deadly hajj-related incidents:

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2015: At least 107 people are killed and scores wounded when a crane collapses in bad weather, crashing onto the Grand Mosque in Mecca, Islam’s holiest site.

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2006: More than 360 pilgrims are killed in a stampede at the desert plain of Mina, near Mecca, where pilgrims carry out a symbolic stoning of the devil by throwing pebbles against three stone walls. The day before the hajj began, an eight-story building being used as a hostel near the Grand Mosque in Mecca collapsed, killing at least 73 people.

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2004: A crush of pilgrims at Mina kills 244 pilgrims and injures hundreds on the final day of the hajj ceremonies.

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2001: A stampede at Mina during the final day of the pilgrimage ceremonies kills 35 hajj pilgrims.

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1998: About 180 pilgrims are trampled to death in panic after several of them fell off an overpass during the final stoning ritual at Mina.

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1997: At least 340 pilgrims are killed in a fire at the tent city of Mina as the blaze was aided by high winds. More than 1,500 were injured.

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1994: Some 270 pilgrims are killed in a stampede during the stoning ritual at Mina.

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1990: The worst hajj-related tragedy claims the lives of 1,426 pilgrims in a stampede in an overcrowded pedestrian tunnel leading to holy sites in Mecca.