Chemring Group PLC says they expect to lose around £20 million after a fatal explosion at their factory near Salisbury.
One employee was fatally injured and another is still receiving treatment in hospital.
The Chemring Countermeasures branch has been assessing how Friday's incident will impact their business.
The group previously anticipated the final quarter profits at £55million but have reassessed and expect the figure to reduce by £10-20million.
The union Unite have criticised how quickly the firm have looked at the financial impact of the explosion.
Unite regional legal officer Stuart Davies spoke to ITV West Country:
An investigation is underway to find out what caused the incident at approximately 5pm on Friday 10th August in the flare manufacturing plant.
CCM has suspended production and a further update is expected when the group publishes its next trading statement on 4 September 2018.