The condition of the existing cables on the bridge have to date been monitored acoustically.
However, the anchorages, where the main cables are attached to concrete-filled tunnels bored into the rock on each shore, will require more intrusive investigation.
This warning forms part of consultant WA Fairhurst's ongoing investigation into the feasibility of replacing or augmenting the capacity of the Forth Road Bridge's main suspension cables.
"It was always going to be difficult to prove the structural integrity of the anchorages because of their unique construction," said Forth Estuary Transport Authority general manager and bridgemaster Alastair Andrew.
"We're going to have to carry out intrusive investigations and possibly even load test individual elements," he said.
"I would emphasise there are no safety concerns at this time – this work is purely to give reassurance that there are no hidden problems."
WA Fairhurst’s study indicates that replacing or augmenting of the main cables is technically achievable, but would mean years of delays on the region’s strategic road network. Conclusion of the study will be published in February 2008.