The administrative action, filed with the U.S. Department of Agriculture last week by the Physicians Committee for Responsible Medicine (PCRM), says that based on records obtained by the group, 15 of 23 monkeys that received brain implants made by Neuralink later had to be euthanized. PCRM accused the company of subjecting the monkeys to “extreme suffering.”

Neuralink, in a blog posted to its website yesterday, acknowledged that eight animals had to be euthanized during the time it was conducting animal-based research at the University of California at Davis. But the company denied that any of the animals involved in its research experienced extreme suffering.

The company said in its blog post that two of the animals were euthanized “at planned end dates” in order to gather key data that could only be obtained by autopsy. The other six animals, it said, were euthanized on the advice of UC Davis veterinary staff after developing a variety of complications, including four cases of infection related to having the device implanted, one complication that involved a bad reaction to the surgical glue used to seal the incision, and one case where the brain chip failed after implantation.

Neuralink has since moved its animal research from UC Davis to its own, purpose-built animal research facility at its headquarters in Fremont, Calif.

“All animal work done at UC Davis was approved by their Institutional Animal Care and Use Committee (IACUC) as mandated by Federal law, and all medical and post-surgical support, including endpoint decisions were overseen by their dedicated and skilled veterinary staff,” the company said in its blog post.

PCRM said in a statement that Neuralink’s blog posting “fails to acknowledge the significant pain and distress experienced by monkeys used and killed at UC Davis,” and that based on the animal records that the group obtained, it appears that “In some cases, the animals suffered for months before they were euthanized.”

“Neuralink’s recent blog post defending its use of 23 monkeys for surgical brain implant experiments doesn’t change the horrific treatment that the public records reveal,” a PCRM spokesperson said. “Monkeys used by Neuralink at UC Davis did have portions of their skulls removed and devices screwed to their skulls.”

PCRM’s administrative action against Neuralink and UC Davis was based on animal records that the group obtained via a separate lawsuit filed in California Superior Court last May against the university. That lawsuit alleged that UC Davis failed to release certain records related to the test monkeys despite a California Public Records Act request. UC Davis eventually gave PCRM medical records on the test monkeys, which the group said indicates that alleged animal abuse. PCRM has since filed an amendment complaint against UC Davis alleging that the university is
withholding videos, photos, and ID records that could corroborate the group’s claims of animal abuse.

A UC Davis spokesperson previously told Fortune in a statement that its partnership with Neuralink ended in 2020 and that the university’s Institutional Animal Care and Use Committee “thoroughly reviewed and approved” the research protocols of that project. The spokesperson added that “animal research is strictly regulated, and UC Davis follows all applicable laws and regulations including those of the U.S. Department of Agriculture.”

Update, Feb 15, 2020: This article has been updated with a comment from PCRM.