A few broken steel wires and varying levels of corrosion have been found in the Forth Road Bridge's support cables.
The bridge is now 40 years old
The discovery was made during the first full-scale cable inspection in the bridge's 40-year history.
Forth Bridge manager Alastair Andrew said there were no safety concerns and stressed that just 22 broken wires had been found out of 11,618.
Internal inspections at five more points will take place between now and next spring.
The results of the inspection were disclosed at a meeting of the Forth Estuary Transport Authority (FETA) Board on Friday.
Mr Andrew told board members that engineers had found a few broken wires and varying levels of corrosion inside the cables.
He stressed that work was at a preliminary stage and there was no need for drivers using the bridge to have any concerns over safety.
Mr Andrew said: "I can't emphasise enough that safety is not an issue at this time.
"Neither would I like to be accused of raising unnecessary fears - I am simply stating the fact that early, visual inspections at three locations have revealed some broken wires and levels of corrosion that require further laboratory analysis."
He added that the matter had to be put "into perspective".
Mr Andrew said there were 11,618 high-tensile steel wires making up each main cable on the bridge.
At the worst location, he said 22 broken wires were found - representing less than a fifth of one percent of the total.
He also said that samples from three locations were being tested to establish the significance of the corrosion.
During the inspection, contractors opened the steel outer protective casing of the cables for the first time since the suspension bridge opened.
Mr Andrew told the board that there were no guides available in the UK or Europe as to how to carry out this kind of inspection.
But he said that FETA had adopted a US-guide which recommends that cables more than 30-years-old should be opened up for inspection.
He added: "The cable will be inspected at a total of eight locations, four at low level and four closer to the tower tops.
"It is expected the lower inspections will be completed by November. Because of high winds at the tower tops, the remaining four high-level locations will be inspected from April next year.
"A clearer picture will only emerge as the inspection programme progresses and the visual inspections are supplemented by laboratory analysis which is under way.
"FETA will, of course, keep the public fully informed of developments. We are an open and accountable organisation."