Part of Clacton Pier has collapsed into the sea during structural work to prepare for the installation of a new rollercoaster.
Nobody was injured when the “small section of the outside ride deck” gave way on Friday, a spokesman for the Essex attraction said.
The work was to install new concrete decking in an area currently closed off to the public.
Pier director Billy Ball said: “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, which is now fenced off.”
He said that around 4,000 square metres of work has been carried out and this area involves 140 square metres.
“As part of our ongoing commitment to ensure the pier remains safe and serviceable, we go to extensive lengths to analyse and calculate the integrity of the existing structure before constructing any new attractions,” he said.
“Our structural engineers are currently assessing the situation.”
The affected section of the ride deck was part of an area which had been set aside for the new Looping Star rollercoaster ride, which is due to be opened in the spring.
Clacton Pier was officially opened in 1871 and was lengthened in 1893 with the addition of a theatre and pavilion, its website says.