Saudi Arabia has begun an investigation after a crane collapsed in the Muslim holy city of Mecca, killing at least 107 people, reports BBC.The huge red crane crashed into a part of the Grand Mosque - which was filled with worshippers at the time.The inquiry is taking place as criticism grows over safety standards at the holy site.It is unclear how many of the victims were killed by the collapse or the stampede that followed it.At least 230 people were injured in the incident.The collapse happened at 17:23 local time (14:23 GMT) on Friday.The head of Saudi Arabia`s civil defence agency, Lt Sulayman Bin-Abdullah al-Amr, said strong winds and heavy rains caused the crane to fall.Mecca is currently preparing for the annual Muslim Hajj pilgrimage.Thousands of people are expected to arrive in the Saudi city from all over the world later this month.Lt Amr said the city had been hit by unusually high levels of rainfall and winds of up to 83kph (50mph) shortly before the crane came crashing down.Videos posted online showed the moment the structure collapsed, with a loud crash followed by panic and shouting. Bodies and blood could be seen on the floor of the mosque.Lt Amr said an investigation was being carried out to assess the damage, and the "extent of the safety of these sites".Irfan Al-Alawi, from the Islamic Heritage Research Foundation, told the BBC that the Grand Mosque is currently surrounded by 15 large cranes amid major redevelopment work."The entire area is like a salvage yard," Mr Al-Alawi said."Saudi Arabia has to re-think its health and safety strategy," he said, "as there were 800,000 people in the mosque area at the time of the accident."Mecca is preparing to welcome about two million Muslims from around the world for the Hajj, which begins in about 10 days` time.Islam requires that every Muslim capable of doing so performs a pilgrimage to the site at least once in their lifetime.Saudi authorities began a major expansion of the site last year to increase the area 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.More than three million people undertook the Hajj pilgrimage to Mecca in 2012. Saudi authorities have taken steps since 2013 to limit the number of people involved.Large numbers of people have resulted in several tragedies over the years.