An HSE spokesperson said that the cause of the accident ought to be established fairly quickly.
He said the type of the crane involved would not be in operation while the investigation was being carried out. He added that the accident was not related to the crane collapse that occurred in February. This led to the death of PC Harrington worker Patrick O'Sullivan.
Building revealed last month that quantity surveyors employed by Australian firm Multiplex, the main contractor at Wembley, had warned the company directors six months ago that they had serious safety concerns over PC Harrington, the concrete contractor on the stadium.
Multiplex said that the minutes of the meeting did not reflect the view of Multiplex.
The HSE is also considering the possibility of sabotage in connection with the death of O'Sullivan.