A police spokesman said last night: "Merseyside Police and the Health and Safety Executive are carrying out joint investigations initially until it is determined whether the incident was an industrial accident or a result of criminal activity."
The incident caused traffic chaos around Princess Way, a busy dual carriageway, and the road was closed for several hours.
The victim, who has not yet been named, is the second man this month to be killed after falling from a cherry picker on Merseyside.
On August 1, Ian Shacklady fell from the top of his cherry picker while pruning trees in the grounds of Saint Agnes's Church in Huyton, as his son watched helplessly from the ground.