The commissioner of the U.S. Food & Drug Administration visited the National Center for Toxicological Research in Jefferson Thursday to address the deaths of four squirrel monkeys last year that were part of a research project on the effects of nicotine addiction.

The deaths were made public in late January.

In a news release, Dr. Scott Gottlieb said he met with the facility’s director, Bill Slikker, and his senior management team, and “I know that the entire NCTR team is fully committed, along with me, to taking whatever corrective steps we can as an agency to improve our research enterprise.”

“As an agency, we always face challenges, and we’ve faced some significant ones over the last several months in relation to a research study that was being conducted at NCTR,” Gottlieb said in the release.

“Although the questions asked by this research were important, the findings from our assessment of the conduct of that study raised concerns that required our intervention. Those findings have called upon us to strengthen our animal research programs across the agency. Together, we committed to take steps to address the concerns identified around this study — some of which were related to NCTR’s third-party animal welfare contractor — and ensure our continued ability to conduct critical scientific research at FDA that’s held to the highest standards. We outlined those steps recently in our statement permanently ending the study.”

Gottlieb added:

“I want to be clear on one thing: The issues related to this study do not diminish my confidence in NCTR, nor lessen my strong commitment to their ongoing work and the studies that we’ll continue to solicit. My concerns were related to this one study.

“It also does not change my support for the critical public health role that NCTR plays. There’s no question that Bill Slikker and his team were deeply committed to the assessment of this study’s conduct and remain devoted to the welfare of animals and the integrity of their research programs in support of FDA’s mission. My visit to NCTR affirmed my confidence in their ongoing research and their high ethical standards.”

The FDA said the nicotine study was immediately put on hold in September when agency officials learned the four monkeys had died at the National Center for Toxicological Research. Three of the monkeys died because of complications involving anesthesia, and one death was related to bloat, the cause of which can be unclear, said Tara Rabin, an FDA spokeswoman. Rabin said she didn’t know when the monkeys died.

The study began in 2014 with two dozen male monkeys, half adults and half adolescents, according to documents on the FDA’s website.

Renowned primate researcher Jane Goodall wrote to the agency Sept. 7, saying the center’s treatment of monkeys was “tantamount to taxpayer-funded torture.”

“I was disturbed — and quite honestly shocked — to learn that the U.S. FDA is still, in 2017, performing cruel and unnecessary nicotine addiction experiments on monkeys,” Goodall wrote.

She said devices were placed in young monkeys to deliver nicotine directly into their bloodstreams. The animals were then put in restraint devices and trained to press levers to receive nicotine doses, Goodall wrote.

“To continue performing nicotine experiments on monkeys when the results of smoking are well-known in humans — whose smoking habits can be studied directly — is shameful,” she wrote.

Gottlieb said in the news release that “The deep commitment that our colleagues at NCTR share to science and animal welfare was evident to me during my visit. Research involving live animals, and especially primates, is a small but important part of the critical scientific work done at NCTR. The institution has been involved in many of the significant scientific findings of modern times, particularly work aimed at informing the safe use of products and exposing the risk of toxicological dangers.”

Gottlieb went on to say that “Many lives have been saved owing to the discoveries revealed by scientific work begun at NCTR. The impact that the science of NCTR has had on human and animal health cannot be overstated. Among the many world-class programs underway at NCTR right now for which I’ve been briefed on include biomarker identification, bio-imaging, nanotechnology and personalized medicine.

“NCTR’s work on pediatric anesthetic use — and their discoveries related to the short and long-term effects of anesthesia on adolescent brains — have changed the practice of medicine and made pediatric surgery safer. This work will alter the course of the lives of many children for many generations. NCTR’s work to evaluate drug residue from the veterinary use of antibiotics has similarly changed public health.

“These are just a few of the many achievements of NCTR. I’m proud of these achievements. I’m proud of the people of NCTR and their commitment to science and the public health. I’m proud to be Commissioner of an agency that counts an institution as special as NCTR as part of its enterprise. And I’m proud of the prompt and passionate way in which the leadership of NCTR, and those involved in primate research, sought to assess the challenges related to the study that was recently ended; and the concern they showed for animal welfare and the scientific process.”