Hi Aparna,
I think taking any drastic actions suddenly would affect the employees feelings as it would be like a sudden cultural shock for them. I think in manufacturing the things should be taken with proper sensitiveness. You should have continuous facts in hands to pin point anyone.
I think you can try the following:
1. Identify the job types these people are engaged into (I think you would have it already).
2. Sit with a person or your boss who know all these job types well and define the KRA or KPIs.
3. Start measuring these on a day-to-day or weekly basis through a dashboard. Train people on how to interpret these.
4. Internally you also keep track of which day the boss was there and which day the boss was not there in the office.
5. With the data in point no 4, you can discuss with employees that you've observed that the productivity goes down when boss is not there in office. Please put the dashboard and show compare productivity among all job types. This will inculcate a feeling of who was better. Also, it will not put blame on a single person rather it will be for all the people involved in that job type.
This will also put a feeling of belongingness to a team where in they will try that their team's productivity should not be down next time.
6. Reward the teams which are having the highest productivity. Reward the best performers from the team also (if you develop a mechanism to measure performance at individual levels).
7. You can also do some short team building trainings.
Think over these lines and then you can decide what suits best for your organization.
Regards,
Yogesh