Poppy seed bagels and muffins could cause U.S. service members to fail a drug test, the Pentagon warned in a memo last week. 

Gilbert Cisneros, the Under Secretary of Defense for Personnel and Readiness, told military leaders in a Feb. 17 letter that the consumption of poppy seeds could interfere with drug testing. 

A young woman opens a poppy pod to reveal the seeds inside at a farmer's poppy field on July 22, 2018 Podkozi, Czech Republic. (Sean Gallup/Getty Images)

"Concerns with poppy seeds and drug testing are not new," Cisneros wrote, noting that seeds may be contaminated with morphine and codeine during harvest. 

"Recent data suggests that certain poppy seed varieties may have higher codeine contamination than previously reported. Consumption of poppy seed products could cause a codeine positive urinalysis result and undermine the Department’s ability to identify illicit drug use."

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The Department of Veteran Affairs raised testing levels for opiates from 300 ng/mL to 2000 ng/mL in 2017 due to the potential for false positives from poppy seeds. 

Poppy seed rolls are seen at a bake sale. (Paul Weaver/SOPA Images/LightRocket via Getty Images)

Poppy seeds are common in baked goods like bagels, cakes, and muffins, as well as other food like salad dressing and granola. 

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"Out of an abundance of caution, I find protecting service members and the integrity of the drug testing program requires a warning to avoid poppy seeds," Cisneros wrote in the memo. 

"As more information becomes available we will revise this policy accordingly."