Meury fired off a letter with his concerns to Dante Labs and received a response within a few days acknowledging the mistake.

Dante Labs’ CEO Andrea Riposati said he’s now aware of five people receiving used kits, including Meury, after looking into the matter. Ten customers have received fresh kits and a refund.

In an email to CNBC, which the company subsequently posted to its blog, Riposati said the start-up used a third party to ship the saliva collection kits and return them using a UPS or FedEx prepaid shipping label.

“For five orders, this partner printed the wrong return shipping labels and received the five kits back in its facility. Then, the partner managed these used kits as new units and fulfilled five new orders with them,” he said.

Riposati said the used kits did not disclose any personally identifiable information, so it didn’t violate customers’ privacy.

The company didn’t name its third party provider, stating that it took “full responsibility” for the mistake. It also stressed that its overall error rate is 0.5 percent, which it admitted is still “too high.”

The market for DNA testing has exploded in the past decade, with consumer demand increasing and costs continuing to plummet. Researchers expect that the global consumer DNA testing market will reach $928 million by 2023.

Many of these companies sell their kits directly to consumers on their own websites, as well as on Amazon, which is making a big push to sell health tests on its marketplace.

But in recent months, several of these companies have come under fire. An investigation from NBC Chicago in April found that at least one provider couldn’t tell the difference between the DNA of a dog and a human. Another from January found widely varying results for different ancestry tests. And in 2017, the feds stepped in when a company tried to give away DNA tests at a football game without the proper licensing.

The site 23andMe in its first years of operations in 2010 admitted to incorrectly processing samples, resulting in up to 96 customers receiving DNA results that were not their own.

“It’s a growing industry with growing pains,” said Robert Green, a medical geneticist at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School.

Green said errors occur even in the best labs, and genetic testing companies are no exception.

But scientists and policymakers are increasingly calling for more regulation to ensure that consumers are making informed decisions and the companies are facing more rigorous standards.

University of Michigan Medical School bioethicist Kayte Spector-Bagdady said sending used samples to customers raises questions about the validity of results and whether the company is making similar mistakes.

But she’s more concerned ultimately about whether direct-to-consumer DNA testing companies are taking adequate steps to provide accurate health results. “Cases like these might be gross, but it’s not all that different to stepping on a chewed up piece of gum,” she said.