A medical group that opposes medical testing on animals plans to take legal action against Neuralink, the startup founded by Elon Musk to develop brain implants that could act as brain-computer interfaces, the group told Fortune. Central to the group's complaint: allegations that Neuralink and a university with which it partnered on research mistreated monkeys in medical experiments.

The Physicians Committee for Responsible Medicine (PCRM) said that it would file an administrative action on Thursday with the U.S. Department of Agriculture (USDA) against Neuralink and the University of California, Davis, which helped Neuralink conduct its brain computing research on primates. The medical group wants the USDA, which regulates animal research under the Animal Welfare Act, to investigate several instances of alleged mistreatment of monkeys by both Neuralink and UC Davis personnel. That alleged animal mistreatment resulted in chronic infections caused by surgeries, psychological distress, and “extreme suffering,” according to the complaint, which cites animal care records maintained by the university. The complaint asks the USDA to penalize both Neuralink and UC Davis if the alleged violations are corroborated.

A UC Davis spokesperson noted that the university's Neuralink partnership ended in 2020. The spokesperson added that the university's Institutional Animal Care and Use Committee "thoroughly reviewed and approved" the research protocols of its project with Neuralink. "We strive to provide the best possible care to animals in our charge," the UC Davis spokesperson said. "Animal research is strictly regulated, and UC Davis follows all applicable laws and regulations including those of the U.S. Department of Agriculture."

PCRM has publicly advocated against animal testing, and since 2005 it has filed lawsuits against multiple academic institutions, primarily to seek public records about animal experiments. But Neuralink makes an unusually visible target: Its research has grabbed a disproportionate amount of public attention, positive and negative, thanks to its founder’s high public profile. (Call it the Elon Musk effect.) A video of a monkey using a Neuralink brain implant to play the video game Pong, posted on YouTube last April, has already been viewed nearly 6 million times. And last year, Musk said he hoped to begin testing Neuralink’s implants in humans by the end of 2022.

PCRM recently obtained the animal care records related to Neuralink’s research from the university, after it filed a separate lawsuit in California Superior Court last May alleging that UC Davis was withholding the records from the group in violation of the California Public Records Act.

In 2017, Neuralink signed a deal with UC Davis, home to an esteemed primate research facility, for the startup to conduct research for its brain-computer chip technology with help from UC Davis personnel. Since then, Neuralink’s research into surgical implants has involved at least 23 monkeys at UC Davis.

Based on the university’s records, PCRM believes that 15 of those monkeys died or were euthanized as a result of the research, PCRM research advocacy coordinator Jeremy Beckham told Fortune. When the research agreement between Neuralink and UC Davis ended in 2020, the university transferred seven monkeys to Neuralink, he said. (Beckham says it’s unclear what happened to the 23rd monkey, as the records end abruptly in November 2019.)

Despite receiving certain records from UC Davis, PCRM also alleges that the university has withheld videos, photos, and identification numbers related to the monkeys that the group believes will show more evidence that the primates were mistreated. The group plans to separately file an amended complaint in California on Thursday based on its previous May lawsuit, seeking the information it believes was withheld.

The UC Davis spokesperson disputed PCRM's allegations that it withheld information and said, "We fully complied with the California Public Records Act in responding to their request."

Beckham said that one of the UC Davis records details a monkey “who actually collapsed from exhaustion and suffered from seizures,” and that the monkey's caretakers noted that they were videotaping its behavior to monitor its health.

“So we know that these videos and photographs are going to be disturbing, frankly,” said Beckham. “We want to be able to get access to these videos and kind of show people a little bit more of the reality of what it's like inside this Elon Musk–funded laboratory.”

Beckham acknowledged that PCRM opposes all forms of animal testing for medical purposes, and that if it were to investigate other academic institutions researching brain computing that lack the high profile of Neuralink, it “would find some of the same issues.” But he added that PCRM believes UC Davis has an obligation, as a public institution, to reveal the nature of its work with the startup.

“Here you have researchers at UC Davis moving around and operating at the whim of private funding by a billionaire,” Beckham said. “I think it raises some deeper ethical questions here about how these projects are scrutinized,” he added about the animals.

Multiple brain-computing experts have told Fortune that based on the public demonstrations that Neuralink has released so far, the animals involved appear to be healthy. For instance, several sources noted that in the widely viewed “MonkeyPong” video, the primate appeared vigorous and coherent.

Beckham, however, said that the medical records the group has obtained so far “don't seem to match up with what we see in the video that Neuralink and their public relations people are choosing to release.”