In a statement, the city council noted that repair workhad also forced the partial closure of the bridge itself for some hours.
"IP – Infraestruturas de Portugal, which is the entity responsible for the bridge, proceeded to … the controlled removal of the detached concrete, in order to prevent the detachment of new blocks or pieces", the statement reads.
Work was completed late on Thursday morning and traffic was now running again.
The city council and its civil defence officials are to continue to monitor the situation.
The council had closed the road on Tuesday night after pieces of mortar fell from the bridge.
Portugal’s Ministry of Infrastructures on Wednesday said that it was monitoring the situation and that IP had drawn up a "rapid intervention plan" to sort out the problem.
Experts who visited the site confirmed that the material that came off was only surface mortar.
According to the council the bridge, which was built in 1963, has over the decades been subjected to regular maintenance by the state, its owner, but mortar does occasional detach itself “in this type of structure due to various phenomena such as temperature changes."
The bridge, which connects Porto with Vila Nova de Gaia, has been a national monument since 2013.