The collapse occurred last Friday during structural refurbishment work to install a new section of concrete decking.
Pier authorities said “the aim was ensure that the wet concrete being laid would not result in undue structural movement to the existing concrete deck.”
But Pier director Billy Ball said that as this was taking place, excess vertical movement of the piles caused four bays of the existing slab to fail.
He added: “This was being carried out under controlled conditions at a time when the tide was up and no one was under the Pier.
“Site personnel were carefully monitoring the pouring of the concrete when the collapse happened, and everyone was evacuated from that particular area.”
The affected section of the ride deck was a part of the area which had been set aside for the new Looping Star ride due to be opened in the Spring.
Ball said that structural engineers are still assessing the damage and what may have caused it.
No one was injured and the damaged area has been completely fenced off.