MECCA, Saudi Arabia (AFP) - First came the thunder, then the horror.
Witnesses on Saturday described the collapse of a massive construction crane during a vicious thunderstorm a day earlier, an accident that killed 107 people at the Grand Mosque in Mecca, Saudi Arabia, one of Islam's holiest sites.
The red and white crane, one of many that rise up around the mosque to service a major expansion project, toppled into a courtyard of the sprawling compound, where hundreds of thousands of pilgrims from around the world had begun to gather ahead of the annual haj pilgrimage.
"All of a sudden, there were clouds. The sky was filled with clouds and there was strong wind," said Mohammed, a Moroccan pilgrim.
"Suddenly, I heard thunder and then we heard a very loud noise. That was the sound of the crane falling."
Another witness said his car was "shaking heavily from the strength of the wind" at the time.
Qasim, also from Morocco, said prayers had just begun when the rain started, slowly, accompanied by the wind.
"And then we heard thunder. God knows, maybe the thunder hit the crane," he said.
An engineer for the firm carrying out the mosque expansion said the crane's heavy hook, which is able to lift hundreds of tonnes, began swaying.
It pulled the whole crane with it, toppling it into the mosque, said the employee of Saudi Binladin Group.
The screams of victims replaced the prayers that had begun just minutes earlier.
Part of the crane crashed atop an ornate, arched and colonnaded section of the complex, while the rest smashed into the courtyard, gouging out chunks of a floor now stained with the blood of victims.
"If it weren't for Al-Tawaf bridge the injuries and deaths would have been worse," said mosque worker Abdel Aziz Naqoor, referring to the covered walkway which broke the crane's fall, and which surrounds the holy Kaaba.
The Kaaba is a massive cube-shaped structure at the centre of the mosque towards which Muslims worldwide pray.
"We saw people dying before our eyes," the Arab News quoted Sheikh Abdul Raheem as saying.
Ahmed, an Egyptian pilgrim, told AFP he had been on the second floor where some visitors were hurt by falling building blocks.
"Many people were injured and some died. Some fell (from the second floor) onto the main Kaaba area.
"We were very scared, hysterical even. But we managed to get out and help the people who were injured," Ahmed said.