The Food Standards Agency is urging consumers to be on alert for any contamination of Kingsmill loaves.

There have been three complaints from consumers about glass or needles found inside the packaging of the bread since the weekend.

There have also been numerous other reports of other small objects inside the packs.

Police were first called in July last year when pieces of glass and needles were first discovered in packs of Kingsmill products.

The investigation has concentrated on the Allied Bakeries plant in Orpington, which distributes 2.5 million loaves a week and supplies much of the southeast.

Police have taken DNA tests of each of the 300 mostly male staff at the plant and the firm has introduced tamper-proof seals on packaging.

CCTV monitors every aspect of the production and staff are closely vetted. Officers have also been working covertly at the bakery. Checks on staff leaving and entering the building have also increased.

There were concerns about suspicious behaviour of two casual agency workers last year, but they were then barred from the premises.

It is believed that the objects are inserted into the packaging after the baking process. But it is unclear if the tampering is happening inside the factory or in the distribution network.

Baked loaves are carried in large baskets to a separate warehouse inside the premises for packing and then sorted for loading in lorries and vans. All these areas are under surveillance at all times.

One possibility is that someone outside the plant is opening the plastic seals on loaves and concealing the interference with the use of a device to replace the tape.

Other objects that have been found inside packs of breads are chewing gum, plastic discs and a piece of cloth.

Security at food manufacturers is always tight and companies have been particularly vigilant to ensure there is no chance for contamination of the food chain.

There have been no ransom demands or any other communication with Allied Bakeries. A spokesman for the firm, part of the ABF group, said the company was duty bound to report the matter. He said: “We take these reported incidents very seriously. The foreign bodies were clearly visible once the bread bag was opened and were not embedded in the bread. We urge consumers to be vigilant.”

The spokesman said that the company was doing everything to minimise risk of deliberate contamination and to ensure that all products were safe.

• Sainsbury’s has withdrawn a batch of its own-brand Fruit & Nut cereal after moths were found in the product, the Food standards Agency said.

  The problem related to 1.5kg bags of the cereal bearing batch codes beginning with “6213”.

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