Elon Musk’s Neuralink, a medical device company, is under federal investigation for potential animal-welfare violations amid internal staff complaints that its animal testing is being rushed, causing needless suffering and deaths, according to documents reviewed by Reuters and sources familiar with the investigation and company operations.

Neuralink Corp is developing a brain implant it hopes will help paralyzed people walk again and cure other neurological ailments. The federal probe, which has not been previously reported, was opened in recent months by the U.S. Department of Agriculture’s Inspector General at the request of a federal prosecutor, Reuters reported, citing two sources with knowledge of the investigation. It focuses on violations of the Animal Welfare Act, which governs how researchers treat and test some animals.