Officials from the US Department of Agriculture have said they have certified 22 US beef plants to export beef to Japan under a new agreement aimed at satisfying Japanese concerns about mad cow disease.

A further 79 plants have applied for certification in order to meet the 1 September deadline imposed by Japan. Around a half of those applications are expected to be approved by the end of the week, reported Reuters.

The certification assures that meat products have been derived from cattle slaughtered in the US and not Canada. Japan requested such assurances after Canada reported a single case of mad cow disease in May.

Units of Tyson Foods, Excel Corp, Swift & Co and National Beef Packing are among those to gain certification. Companies must provide documents to auditors verifying that a product has been derived from US cattle.