A month-old requirement in Minnesota to blend diesel with a soybean-based additive was suspended last week.

The sale of the blend was halted Friday, Oct. 28, after workers at fuel-blending terminals in the state found that some fuel didn’t meet quality standards set under Minnesota law.

As a result, the Flint Hills Resources refinery in Rosemount shut off all diesel deliveries for 20 hours, The Associated Press reported.

Shortly thereafter, state officials authorized fuel to be sold without biodiesel. Despite the quick action, it took hours to reprogram computers before the refinery south of Minneapolis-St. Paul could resume blending the fuel.

It wasn’t immediately clear if any service stations in the state ran out of diesel.

Gov. Tim Pawlenty signed the one-of-a-kind legislation in September requiring the sale of the biodiesel blend. The law says most diesel fuel sold must contain 2 percent biodiesel.

Minnesota biodiesel is made from soybean oil, but it can be composed from other vegetable oils.

There is no provision in state law that allows the sale of pure diesel if there was a shortage of biodiesel, The AP reported. The Minnesota Department of Commerce authorized refiners, terminals, distributors and retailers to sell pure diesel for 10 days.