The discovery of almonds in three products not advertised as containing nuts has prompted a wider investigation by the Food Standards Agency.
Almonds were found in fajita kits from Morrisons' and Aldi, and in Bart's ground cumin. All three items have been recalled.
The FSA is looking at how the food was contaminated and testing other products containing cumin for nut proteins.
An FSA spokeswoman said there was no evidence at present to link the cases.
The FSA initiated a sampling programme, testing for almond and peanut protein, after certain products containing ground cumin tested positive for undeclared peanut protein in the United States and Canada.
US supermarket Whole Foods has recalled dozens of items that may have contained undeclared peanut, according to the US Food and Drug Administration
The Bart's ingredient was identified through this process and the Morrisons' product through the supermarket's internal testing procedures.
Morrisons' and Aldi's fajita kits are known to share the same supplier.
Professor Chris Elliott, who led the government inquiry into the horsemeat mislabelling that affected British supermarkets in 2013, said it was the first real test of the UK food supply system since the horsemeat scandal.
He told the Independent: "Whenever notifications from the US appear it is a warning to the rest of the world that there is a problem."
All three companies are helping the FSA with their investigation and there is no suggestion they were aware of the issue before testing.
The investigation is focused on products containing cumin, supplies of which are low following crop failures
A spokeswoman for the FSA said: "Currently there is no evidence to link the two alerts on undeclared almond protein, neither is there evidence to link these to the recalls of cumin and cumin containing products in the US."
She added: "The FSA has been proactive in checking for problems with cumin supplies in the UK and will continue to take action to protect consumers."
She said there was no evidence of food fraud at this stage but the Food Crime Unit will become involved if any evidence of a crime emerges.
The Food Crime Unit was set up in the wake of the horsemeat scandal to crack down on fraudulent food entering the supply chain.
There is currently a severe worldwide shortage of cumin, after crops in the major harvest region of Gujarat in India failed.
NHS Choices advises that nut allergies, including peanuts, are relatively common in both school-aged children and adults.
Peanuts are one of the most common causes of fatal allergic reactions to food.