Fallen debris caused a traffic jam on the Queensferry Crossing on Wednesday morning.
Traffic Scotland claimed some drivers ignored the red X lane closure warning sign on lane two southbound as the clean-up got under way.
The alarm was raised at around 7.25am.
Posting on Twitter, a Traffic Scotland spokesperson said: “Lane two of two is closed due to debris on the lane.
“Traffic is ignoring the red X – this is mandatory.”
By 7.50am, the debris had been cleared and all lanes on the M90 crossing were back open.
Drivers were advised that vehicles were backed up to J3 and the tailback “may take a while to ease”.
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