Al Arabiya television earlier said the crane had fallen because of strong storms. Saudi Arabia has been hit by strong sand storms in the last few days.
Saudi authorities have launched a probe into the case, while 15 civil defence and rescue and medical panels have been deployed at the site.
All hospitals in Mecca have been in full alert to receive patients.
The crane fell down because of the bad weather, which was working on the expansion operations at the grand mosque.
The accident happened while the country has started to receive pilgrims from all over the world for the hajj season that will start shortly.
After the conclusion of the current and final expansion, the mosque could accommodate more than 3 million worshipers in one hour.
The expansion aims to accommodate the ever-increasing number of pilgrims from all over the world, especially during Hajj season.(*)