Cadbury owner Mondelez International is planning to close its factory in Dunedin, New Zealand next year.
Security guards were outside every entrance to the popular Cadbury World tourist attraction on Thursday morning and the factory was closed for the day.
Hundreds of workers were called to a meeting and briefed on the proposal to move production to Australia. In a statement, Mondelez said it would invest to redevelop the tourist side of the operation if the local community wanted it to.
Workers leaving the meeting had been told not to comment and had been given media contact cards to show people. They looked shocked and upset.
"I'm gonna get a bottle of wine," said one worker who had been with Cadbury for over 20 years.
The factory employs 350 people and almost three quarters of the products it manufactures are shipped to Australia.
"This is an incredibly difficult announcement, given the factory's proud history and the outstanding performance of our employees," Amanda Banfield, vice-president for Australia, New Zealand and Japan, said.
"Our people in Dunedin are amongst the best performing teams in the region and, if it weren't for their dedication and outstanding performance, the factory might have closed some time ago."
An increasingly competitive industry as well as the factory's distance from its main market were behind the plans, Banfield said.
If the plan goes ahead, the first job loses will kick in late this year for most staff. Mondelez said about 100 people would be kept on until early 2018.
Mondelez said while the manufacturing operations would stop, it was "ready to" invest money to redevelop the Cadbury World tourist attraction to create more jobs and attract more visitors, with a decision due by April.
Dunedin's Labour MPs Clare Curran and David Clark said the closure was a devastating blow.
"The loss of 362 jobs is shattering for the people working there and for the city. I have visited the factory many times and appreciated the warm welcome, kind hospitality, and good cheer of the staff," Clark said.
"These people have been proud to work at this iconic Dunedin institution, and proud to supply products for export with a global recognition. My heart goes out to them."
Curran added that the closure would affect the whole community.
"Employment changes affect mortgages and schooling choices. It is too soon to grasp the flow on effects, but we can be certain this will have a huge impact across Dunedin."