University officials say the alleged poisoning involved routine supply chemicals, not research materials from the influenza institute.
MADISON, Wis. — Police are reviewing a workplace safety incident at the University of Wisconsin-Madison after a staff scientist admitted putting routine lab chemicals into a co-worker’s water bottle and shoes at a campus research institute.
The arrest of Makoto Kuroda, 41, has drawn attention not only to the felony charges filed against him, but also to the safety controls inside a lab where employees work under heightened security rules. UW-Madison said the alleged conduct at the Influenza Research Institute was unrelated to the research done there. The university also said there is no evidence that the incident involved any research materials other than routine laboratory supply chemicals.
Kuroda worked as a staff scientist at the Influenza Research Institute in the School of Veterinary Medicine. Prosecutors charged him April 14 with second-degree recklessly endangering safety and tampering with household products. The criminal complaint says he admitted placing chemicals in items belonging to a co-worker identified as TM. UW-Madison said Kuroda is on administrative leave and that his physical and digital access to university assets has been revoked. His research privileges also were revoked while the university conducts a workplace investigation.
The institute studies viruses that cause illnesses such as flu and COVID-19, according to the university. UW-Madison said all employees who work at the institute, regardless of role, must be approved by the Federal Select Agent Program after an FBI security risk assessment at hiring and every three years after that. The university said it stays in close contact with the FBI and had already contacted the agency after Kuroda’s arrest. Officials also said institute workers receive frequent training on lab protocols, including wearing proper protective equipment.
Police records describe the alleged chemicals as paraformaldehyde, chloroform and Trizol. The university said those substances are routinely found in many research laboratories and said final analysis from the Wisconsin State Laboratory of Hygiene was pending. The complaint says a Trizol mixture used at the institute contains chloroform. A preliminary test found chloroform in residue from TM’s water bottle, with a value so high that test strips could not give an accurate measurement. Police wrote that the reading mattered because chloroform dissipates over time.
The first report reached UW-Madison police April 6. Officer Brock Prough was sent at about 1:13 p.m. to the Influenza Research Institute in the 500 block of Science Drive after chemicals were reported in an employee’s water bottle. A co-worker, AK, told police she smelled the bottle and noticed it seemed off. She also said TM’s shoes smelled of a chemical. TM had not wanted to make a big issue of it, according to the complaint, but AK believed the concern should be reported. The bottle and shoes were secured and kept as evidence.
TM told police he opened a plastic Trader Joe’s water bottle April 2, drank half and left it on his desk. He said he did not drink from it April 3. On April 4, he returned to the office, smelled a bad odor, drank from the bottle and spat out the water because it tasted chemical. On April 6, he returned to work and found the same odor in his office. He traced it to lab shoes kept under his table. TM said the shoes did not leave the institute and did not smell unusual the day before.
The Madison Fire Department Hazardous Incident Team helped process the water bottle April 7. The complaint says firefighters arrived around 2:30 p.m., swept the area where the shoes and bottle had been stored and reported no chemical concern, though their detection meters could not detect chloroform. Deputy Chief Tim Mrowiec took possession of the items for transport to the State Laboratory of Hygiene, according to the complaint. Later that day, police received preliminary results showing the high chloroform reading in water residue.
A second employee, identified as PH, told police chloroform was used for research at the institute and was available in the main lab and annex lab. PH said the chemical was unlocked during the day and locked after everyone left. PH also said all employees had access, that no cameras captured where chloroform was stored or used, and that there were no procedures or records for its use. Those statements appear in the criminal complaint and have not been tested in court. UW-Madison’s broader safety review is separate from the criminal prosecution.
Police said the evidence turned from unexplained odor to confession April 10. Officer Adrian Vera was sent to the institute after a staff member reported that an employee had admitted poisoning another employee’s drink. TM told police Kuroda approached him in the lab, said, “I did it,” and made a comment about his shoes. TM said he was scared and left. A supervisor, YK, told police Kuroda also sent an email in Japanese that said, “I did it. I have also informed the person himself. I am very sorry.”
Kuroda then spoke with police and described the workplace tension behind the alleged act, the complaint says. He said he had met TM at work in 2017, that they had once been friends and that both men had been promoted. Kuroda said TM later received another promotion while he did not. He told officers he believed TM’s attitude changed after that and said TM did not follow lab rules about wearing a coat and goggles. Kuroda also cited hallway conduct and other small workplace moments that he said built up over time.
The complaint says Kuroda described retrieving chemicals from his own work refrigerator on April 5. He said he used a syringe to take paraformaldehyde mixed with Trizol, put about 0.5 milliliters of 4% paraformaldehyde in TM’s water bottle and placed a mixture of Trizol and 4% paraformaldehyde in each shoe. He said he expected TM to get sick and described possible stomachache, vomiting, dizziness, rash and discomfort. “My aim was just, he feel bad,” Kuroda told police, according to the complaint.
Investigators also noted alleged online searches before the incident. The complaint says Kuroda used ChatGPT on his work laptop to look up harmful amounts of paraformaldehyde and Trizol for humans and animals. Police wrote that he looked it up multiple times and that warning pop-ups appeared. When asked whether those warnings made him reconsider, Kuroda said they did not, according to the complaint. He told police he started planning about three days earlier and knew he was going to use paraformaldehyde.
The criminal charges carry significant possible penalties. Second-degree reckless endangerment is a Class G felony in Wisconsin, punishable by up to 10 years in prison and a $25,000 fine. The tampering count is a Class H felony, punishable by up to six years in prison and a $10,000 fine. Kuroda has not been convicted. Public jail records show he was booked April 10, and court records cited in reports said he was placed on a $5,000 bond with restrictions, including no contact with TM and no access to UW-Madison labs.
UW-Madison police said the incident appeared isolated and that there was no known threat to public safety. The department also said the investigation remained ongoing and that additional charges may be filed. The university said employee privacy laws and the active criminal case limit further public comment. Further chemical testing, court filings and the university’s workplace review are expected to determine what more becomes public.
Author note: Last updated 2026-05-06.