A vehicle transporting 100 monkeys to a lab collided with a dump truck in the US state of Pennsylvania, causing several of the animals to escape.
Authorities said on Twitter that four monkeys had "fled the crash scene into the surrounding area." Three were captured, but one was still on the loose as of Saturday morning local time.
The vehicle was transporting Cynomolgus monkeys, also known as long-tailed macaques. The animals can cost up to $10,000 each (€8,800) and have been in demand for coronavirus vaccine research, according to the New York Times.
Local news said a police helicopter with thermal cameras was used to track down the monkeys, while officers on the ground used powerful flashlights.
Residents of the area were advised not to approach the monkeys and to call emergency services in case of a sighting.
The incident took place near the community of Danville, Pennsylvania on Friday afternoon. The shipment of monkeys was en route to a CDC-approved quarantine facility after arriving Friday morning at New York's Kennedy Airport from Mauritius, the US Centers for Disease Control and Prevention (CDC) said.
The CDC said it was cooperating with state police and providing "technical assistance."