Story highlights Witness says crane toppled over during a "sandstorm which turned to rainstorm"

Saudi Civil Defense says via Twitter that storms caused the crane collapse

Mecca's Masjid al-Haram surrounds Islam's holiest site, the Kaaba

(CNN) A powerful storm toppled a construction crane Friday afternoon at the Masjid al-Haram, or Grand Mosque, in Mecca -- killing at least 107 people and injuring 238 others, Saudi Arabia's civil defense authorities said on Twitter.

Photos and video on social media showed the crane crashing through the mosque roof and the aftermath, with bodies, blood and debris spread across the courtyard.

The crane fell 10 days before the start of the Hajj , the annual pilgrimage expected to bring 2 million people to Mecca. The Masjid al-Haram is the largest mosque in the world and surrounds Islam's holiest site, the Kaaba -- a cube-shaped shrine that worshippers circle.

One man said the bad weather contributed to the chaos after the crane toppled over.

"We just washed and were getting ready to head to the Masjid al-Haram for the Maghrib prayer (sunset prayer)," said Yahya Al Hashemi, 30, a CNN iReporter who shot iPhone video of the crane striking the roof of the mosque. "It was a sandstorm which turned to rainstorm and lot of the construction covering boards were flying around, and lots of cracking noises which unfortunately ended with this tragedy. ... Everybody were pushing trying to escape from inside towards the exits."

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