The probe, prompted after glass and sewing needles were found in packs of Kingsmill bread, is believed to be the first in the food and drink industry to use such techniques.
The Metropolitan Police Service confirmed that the factory’s 400-strong workforce had been asked to volunteer for the tests in order to eliminate them from its enquiries. A spokeswoman said that the process was entirely voluntary and that the response from staff had been good. She was unable to confirm how long the process would go on or when the results would be known.
A local representative of the Bakers, Food and Allied Workers Union said that he supported the police’s bid to catch the person or persons involved, but claimed there had been a lack of communication on the matter from Allied Bakeries.