The customer bought a packaged salad from the branch in Gland, in the canton of Vaud, on Monday afternoon, reported 20 Minutes.
She and two friends were starting to eat their food when she spotted half of what looked like a dead mouse in the salad.
“We were disgusted and felt sick. The packet was sealed before the meal. The body must have been packaged up with the food,” she told the paper.
Migrolino confirmed the incident to The Local, saying the paper contacted them itself after the customer found the body of an "as-yet unidentified species”.
In a statement given to The Local, a spokesperson for the supermarket said it had contacted its supplier, which claimed all food safety and quality measures were respected in the making of the handmade salads.
The supplier hadn’t noticed any damage or evidence of rodents in the factory.
“For our supplier, it is unthinkable that this mole or mouse wouldn’t have been noticed during a production process that includes two or even three visual checks,” said the statement.
The supermarket contacted the customer who handed over the offending salad for analysis, the results of which will be available in ten days, said Migrolino.
The supermarket has withdrawn the batch of salads from the shelves across the country and is investigating the incident.
“The safety of its customers and the quality of its products are a top priority for Migrolino,” said the statement.
The supermarket said it will compensate the woman and her two friends for this "regrettable incident".
She is also invited to visit the factory “in order to prove to her that standards are respected all the time”, said the spokesperson.