Traces of a drug used for euthanasia have been found on several dog food products available on the market, prompting the United States' Food and Drug Administration (FDA) to issue a warning to all pet owners on Friday.

According to U.S. FDA, Kibbles 'N Bits, Gravy Train, Skippy, and Ol' Roy are among the many that have been withdrawn by company J.M. Suckers after an investigation led to the discovery of pentobarbital presence in one of their products.

Pentobarbital is a barbiturate that is commonly used in putting down animals.

The announcement came after WJLA-TV, a news station based in Washington D.C, sent samples of various dog food products to an independent lab to get tested for the euthanasia drug.

The investigation found that 60 percent of the tested samples for the dog food Gravy Train came back with positive results.

Although the amount of pentobarbital found on Gravy Train was non-lethal, it is prohibited under the federal law for any concentration of the drug to be found on food products for animals or humans.

In an interview with the HuffingtonPost, a spokeswoman for the J.M. Suckers company said that only Gravy Train tested positive for pentobarbital. But despite this, many products from the company were still pulled out for reasons of caution.

Pentobarbital has been widely used as a euthanasia drug. Small amounts of pentobarbital can cause dizziness, nausea, and drowsiness. However, in high amounts, pentobarbital can induce coma and death.

To see the complete list of products withdrawn by company J.M. Sucker, click here.