A ratification vote for a tentative agreement between the unionized workers at Jamieson Laboratories and the company was rejected on Sunday.
Reports say 67 per cent of the 317 members of Unifor Local 195 voted against the deal.
The workers had been on the picket line for three weeks before the tentative agreement was announced on Friday. They are looking for better pay, job security, and benefits.
Jamieson Laboratories is one of Canada's largest manufacturers of vitamins.
-with files from Adelle Loiselle