The Kenya Bureau of Standards (Kebs) has asked the companies - True Nuts, Fressy, Supa Meal, Nuteez, Sue's Naturals, Zesta and Nutty by Nature - to discontinue and recall any products that are substandard.

Kebs said it carried out tests on the peanut butter produced by these companies and found their aflatoxin levels were higher than the standard.

Aflatoxin is a carconegenic, meaning it can cause cancer.

Nuteez peanut butter was banned from supermarket shelves in January but was declared safe again in April.