At least 87 people have died after a crane collapsed on the Grand Mosque in the Muslim holy city of Mecca, the Saudi Arabian government has said.
More than 180 people were injured in the mishap, the civil defence authority said on Twitter.
Pictures from the scene revealed part of a massive crane that was red crashed through the roof of the mosque. The reason for the failure is not understood.
Mecca is preparing for the annual Hajj pilgrimage that is Muslim.
Hundreds of thousands of folks are likely to arrive in the Saudi city from all over the world later this month.
Reports indicated the crane fell following rain and high winds. The Arabian peninsula has been has been hit by strong sand storms over the past week.
A video posted on YouTube, which could not be independently verified, seemed to record the second the crane fell, using a loud crash heard in the background followed shouting and by panic.
Images circulating on Twitter seemed to show numerous bodies and blood on the ground of the mosque.
Saudi authorities began a significant growth of the site this past year to boost the part of the mosque by 400,000 square metres (4.3 million square feet), to allow it to accommodate up to 2.2 million people at once.
The crane that fell on Friday was one of a number dotted around the site as part of the building job.
The mosque is the destination for countless Muslims undertaking the Hajj pilgrimage each year and Islam’s most sacred site.
At the heart of the mosque is the Kaaba, a black cube-shaped building which Muslims all over the world face when they pray.