Emergency services were called to the packing supply warehouse on Liberty Road in Huntingwood and arrived to find the 65-year-old man was no longer trapped but had serious injuries, NSW Ambulance Inspector Andrew McAlpine said.

"[He] was released by co-workers, he was in a life-threatening, critical condition," said the inspector, who was at the scene.

Mr McAlpine said the first paramedics provided "life-saving interventions" straight away, before the man was taken to a medical team who had arrived by helicopter.

'The patient was then placed in an induced coma, further stabilised and transported urgently with police escort to Westmead Hospital in an extremely critical condition," Mr McAlpine said.

The inspector said the man had injuries to his chest wall and multiple fractures.

A Westmead Hospital spokeswoman said the man was in a critical but stable condition on Wednesday afternoon.

Early reports suggest the accident occurred when the man was picking up a piece of wood while another worker was moving a shipping container, Mr McAlpine said.

The man was injured at a Sydney warehouse of industrial packaging company WRS Orora .

A company spokesman said staff members were working with emergency services and were co-operating with relevant authorities and regulatory agencies as the incident was investigated.

"Orora will also conduct a full investigation into the incident," the spokesman said in a statement.

"Safety is the number one priority at Orora and we remain committed to providing a safe workplace for our team members.