Passengers and crew had to be evacuated from the 6.40am service following the discovery on Saturday morning.
P&O Ferries announced that sailing was being cancelled and told customers there would be lengthy delays to later crossings.
However following the arrival of the Port of Dover police it was confirmed shortly after 10.15am that it was a false alarm.
“A suspicious package was found on one of our ships this morning and all passengers and non-essential crew were evacuated as a precaution,” said a spokesman for P&O Ferries said in a statement.
P&O warned customers that the disruption was causing delays of up to 120 minutes. The 7.25am service was scheduled to leave at 10.45am, while the 9.25am ferry was delayed to 11am.
Pictures from the Port showed customers waiting in the terminal building following their evacuation from the ferry. Security staff, police vehicles and a bomb disposal van attended the scene.
“We apologise for the inconvenience caused,” P&O tweeted to customers.
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