The National Zoo says it’s had to temporarily close its Kids’ Farm exhibit—essentially a petting zoo—because of E. coli.

In a release issued on Monday afternoon, the Smithsonian facility explains that on Feb. 18, a “routine fecal screening process” for goats showed signs of the bacteria. Although the goats were then removed from public view, follow-up tests confirmed E. coli in four goats and one cow last Friday. “Based on these results, the Kids’ Farm was immediately quarantined and staff started appropriate protective measures, including treating all the farm animals with antibiotics,” the zoo says. The exhibit will reopen after zoo vets get “three consecutive weeks of negative test results.”

“As most people know, E. coli is everywhere in our environment,” Brandie Smith, an associate director at the zoo, explains in the release. “Because it is so common, we routinely test our animals. It’s unfortunate that we have to close the Kids’ Farm temporarily, but we’re taking the right preventative measures for our guests, staff and the animals.”

The U.S. Department of Agriculture and D.C.’s Department of Health are assisting the zoo with next steps. The latter says the goats and cow could have gotten the pathogen “from a wild animal, from humans, or through a food source.” Currently neither staff nor the animals are showing signs of disease related to an E. coli infection.