Do you know what’s in your boba? Typically, boba, or tapioca pearls, are made up of tapioca starch and brown sugar, but a recent investigative report in China found allegations that some of the country’s boba may contain leather and rubber.

According to the Hong Kong Free Press, a Qinqdao reporter for broadcast station Shandong Television drank a boba milk tea from a local shop. A CT scan taken of the reporter’s stomach at a local hospital afterward revealed the tapioca pearls lay undigested.

In the segment run on the program “Life Help,” scientists from Qingdao University’s Chemical Experimentation Center analyzed the purported tapioca pearls and were reportedly unable to confirm its make-up. They described the pearls as “highly adhesive.”

Undercover interviews with local boba tea shop managers found that they also seemed unsure of the pearls’ actual ingredients. One manager, however, made a stunning accusation that would mean illegality committed on the part of the boba manufacturer if true: “They’re all made at chemical plants. To put it bluntly, they’re made from the soles of leather shoes and old tires.”

While boba tea has seen heavy popularity growth stateside over the last decade, the Taiwanese-born drinks have also seen their fair share of controversy. In addition to several scandals in the Philippines and Taiwan over unapproved and toxic additives in tapioca pearls over the last several years, a 2012 German study found that some boba contained carcinogenic “PCB-like” substances.