QAF, a maker of bread, bakery and confectionery products, said an ammonia leak occurred at its Fishery Port Road warehouse on January 26, resulting in a halt of operations at the premises.
The leak at the warehouse was shut off by the Group and employees were evacuated prior to the arrival of the Singapore Civil Defence Force, the company said in a statement on Tuesday.
Four employees were taken to the hospital, and all have since been discharged, the statement said.
The warehouse was used by the company's subsidiary, Ben Foods, for storage of food and beverage products.
BFS is a distributor of third-party and proprietary-brand food and beverage products to the foodservice industry.
A stop work order has been issued by the Ministry of Manpower under the Workplace Safety and Health Act to cease carrying on works at the premises until certain measures are taken, the company said.
The Agri-Food & Veterinary Authority of Singapore is also looking into the matter.
QAF said it was in discussion with the relevant authorities with a view to resuming operations.
Shares in QAF were down 0.9 percent at S$1.14 on the Singapore Exchange. The stock has lost about 19 percent in a year.