HEIDELBERG, Miss. (AP) — Three monkeys remained on the loose Wednesday as searchers in masks, face shields and other protective gear scoured fields along a rural Mississippi highway where a truck carrying the primates overturned a day earlier.

It remained unclear who owns the monkeys, who was transporting them and where they were being taken when the truck crashed on Interstate 59 north of Heidelberg. Authorities have said most of the 21 monkeys were killed but haven’t elaborated on just what occurred.

The Jasper County Sheriff’s Department has said animal experts from Tulane University examined the trailer Tuesday evening and determined three monkeys had escaped.

The truck was carrying Rhesus monkeys, which typically weigh about 16 pounds (7.2 kilograms) and are among the most medically studied animals on the planet. Video recorded after the crash showed monkeys crawling through tall grass beside the interstate, where wooden crates labeled ā€œlive animalsā€ were crumpled and strewn about.

The truck was no longer at the scene Wednesday, but the searchers in gear including white coats, gloves and hair nets were checking fields, aided by law enforcement officers.

Jasper County Sheriff Randy Johnson said Tulane officials reported the monkeys were not infectious, despite initial reports by the truck’s occupants warning that the monkeys were dangerous and harboring various diseases. Nonetheless, Johnson said the monkeys still needed to be ā€œneutralizedā€ because of their aggressive nature.

A black trailer with ā€œMississippi Department of Wildlife, Fisheries and Parks Mobile Commandā€ written on the side of it. It is hitched to a black truck.
The Mississippi Department of Wildlife, Fisheries and Parks set up a mobile command in Heidelberg, Miss. on Oct. 25, 2025. AP Photo/Sophie Bates

Leslie Tate, assistant director of communications at the Tulane National Biomedical Research Center, where the monkeys originated, told the Mississippi Free Press that the institute could not provide information on where the monkeys were bound for, or any details about the specific route their transport took. Tate provided a statement from the center, and declined a request for an interview with an official from Tulane.

ā€œNonhuman primates at the Tulane National Biomedical Research Center are provided to other research organizations to advance scientific discovery,ā€ Tate wrote. ā€œThis is a common practice among research organizations. On Oct. 28, a vehicle was transporting 21 Rhesus Macaques when an accident occurred on I-59 in Mississippi. The nonhuman primates were not being transported by Tulane, not owned by Tulane, and not in Tulane’s custody.ā€

The statement continued. ā€œThe primates in question were not carrying any diseases and had received recent checkups confirming that they were pathogen-free. Although Tulane did not transport or own the nonhuman primates at the time of the incident, we sent a team of animal care experts to assist in this tragic incident. Questions regarding the missing nonhuman primates and other details of this case should be referred to the Mississippi Department of Wildlife, Fisheries, and Parks.ā€

The monkeys were being housed at the Tulane University National Biomedical Research Center, which routinely provides primates to scientific research organizations, according to the New Orleans school. The research center is located in Covington, Louisiana, about 40 miles (65 kilometers) north of New Orleans.

All other monkeys were being transported back to Louisiana.

A monkey emerging from the back door of an overturned white truck trailer
A transport truck containing research monkeys overturned on Interstate 59 near Heidelberg, Miss., with some of the primates escaping their containment on Oct. 28, 2025. Photo courtesy Jasper County Sheriff’s Department

About 10 years ago, three Rhesus macaques in the breeding colony of what was then known as the Tulane National Primate Research Center were euthanized after a ā€œbiosecurity breach,ā€ federal inspectors wrote in a 2015 report. The breach involved at least one staff member failing to adhere to biosafety and infection control procedures, it said.

The facility made changes in its procedures and retrained staff after that happened, according to the report from the U.S. Animal and Plant Health Inspection Service. Earlier this year, Tulane made a slight change to the name of the facility, replacing ā€œPrimateā€ with the word ā€œBiomedical.ā€

The Mississippi Highway Patrol said Wednesday that it was investigating the cause of the crash, which occurred about 100 miles (160 kilometers) from the state capital, Jackson.

Dr. James Watson, Mississippi’s state veterinarian, verified that the animals had the proper documents and ā€œcertificate of veterinary inspectionā€ for legal transport across state lines, he said in an email to The Associated Press. The state’s Board of Animal Health wasn’t involved in the response to the crash, and additional information would need to come from Tulane, he said.

If anyone sees monkeys, they should call the authorities and shouldn’t approach the animals, the sheriff’s office has warned.

Rhesus macaques “are known to be aggressive,ā€ according to the Mississippi Department of Wildlife, Fisheries and Parks. It said the agency’s conservation workers were working with sheriff’s officials in the search for the animals.

The search comes about one year after 43 Rhesus macaques escaped from a South Carolina compound that breeds them for medical research because an employee didn’t fully lock an enclosure. Employees from the Alpha Genesis facility in Yemassee, South Carolina, had set up traps to capture them.

___

Associated Press Writer Jeff Martin in Atlanta contributed.

Mississippi Free Press reporter Nick Judin in Jackson contributed.

Sophie Bates is The Associated Press's new video journalist in Mississippi. Sophie joins from the ABC affiliate in Toledo, Ohio, where she works as a multimedia journalist. Sophie is an aggressive reporter whose role in Ohio is a mix of breaking news and deeper off-the-news investigative stories. She recently worked on a five-part investigative series on homelessness and affordable housing in the Toledo area.

Since 1846, The Associated Press has been breaking news and covering the world's biggest stories, always committed to the highest standards of accurate, unbiased journalism. The Associated Press was founded as an independent news cooperative, whose members are U.S. newspapers and broadcasters, steadfast in our mission to inform the world.