The port remains open though the decision has led to changes in the sailing times of some ferries.
The HSE investigating team, which included metallurgists, was focusing its inquiries on a broken hinge which linked the 56ft high walkway. The team has been joined by engineers from Feab, the structure's Swedish manufacturer.
Parts of the walkway had been taken away for forensic examination. The results of the investigation, which the HSE said would be made public, will not be known for several weeks.
The six people who were killed included a Briton, named as Steven Jones, a lorry driver from Northern Moor, Manchester, who was travelling with a friend who suffered multiple fractures. The other dead included two Belgian men aged 42 and 25, an Italian woman aged 24, and a Frenchman aged 26.
The six other people injured were described as stable and comfortable although several will require surgery for broken bones.