Forth Road Bridge carriageway closed due to steel defect
The southbound carriageway of the Forth Road Bridge has been closed as a safety precaution after a defect was discovered in the steelwork.
Bridge operators Amey said the problem was found during a routine inspection.
A contraflow is in place on the northbound carriageway to allow a single lane of traffic to flow in each direction.
Engineers were due on site at first light on Wednesday morning to do a more detailed assessment of the damage.
Motorists were warned to expect "very long delays" and avoid using the bridge if possible.
Mark Arndt, operating company representative, said: "We've taken the decision to close the southbound carriageway as a safety precaution after one of our engineers spotted a new defect to a piece of steelwork.
"Unfortunately this defect is located in a particularly hard to access area so the full detailed inspection cannot safely be carried out in darkness or during high winds. Our inspectors will however be monitoring the situation overnight and we will be ready to move in as soon as conditions allow.
"We apologise for the short notice to these essential traffic restrictions and are aware that they will result in very long delays, so our advice is to avoid Forth Road Bridge and divert via Kincardine or the A9 and M9, use public transport or travel outwith peak times."
Amey said it would provide further updates when there was new information.
The company said it sympathised with drivers who would be affected by the closure, but that "safety must come first".
A new £1.4bn Queensferry Crossing over the Firth of Forth is due to open in December next year.
It was ordered by ministers because of corrosion of the main suspension cable on the Forth Road Bridge.