I have a relative who works in a factory that makes biscuits and sweets (large well known company). They make them for Tesco, Marks and Spencer etc.
You would not believe how strict they are in the factory and what you can and cannot do.
For example, anyone who comes into the factory chewing gum is sacked. If chewing gum falls in the production line it is untraceable and the whole line has to be closed down and cleaned out. It can cost the company thousands.
Most jewelrey is banned, and everyone has to wear hair nets and overalls. If a man has a beard or moustache they have to wear a face mask.
Anyone who goes out of the factory to go to lunch or to the loo has to remove all their protective clothing, and then when they come back put it all on again.
If this mouse was found in the bread it shows poor hygine controls.