A truck carrying 100 monkeys crashed along a highway in eastern Pennsylvania on Friday, after colliding with another large vehicle on the road, resulting in several monkeys escaping their crates, local media reported.
The local ABC station said state police and game wardens located one of the escaped monkeys perched on a tree near the accident site but that three others remained loose in the area as of late Friday night, and as temperatures were set to drop to below freezing.
The crash occurred around 3:30 pm local time (2030 GMT) near the rural township of Danville about 125 miles (200 kilometres) northwest of Philadelphia.
The cynomolgus monkeys are often used in laboratory research and were being transported to a lab in Florida when the crash occurred, the New York Times reported, citing Pennsylvania State Police said.
An NBC news station said local authorities were instructed to secure the area for the US Centers for Disease Control and Prevention and the Pennsylvania Department of Health.
By nightfall, Pennsylvania State police and the State Game Commission were actively searching for the escaped monkeys including with the aid of a helicopter using thermal cameras, the local ABC news station said.
The station said state police shared a nighttime photo of the monkey that was seen perched on a tree and that searchers used flashlights to focus on the tree and nearby brush.
"We later heard three shots ring out. It's unclear what type of weapon was used and we're not sure where the monkey is or its condition," a WNEP reporter wrote on the station's website in a late night story update.
The WNEP website said investigators left the scene shortly after the fired shots were heard and that there was no immediate word on the condition of the monkeys or whether they had even been found.
PAHomepage said officials were warning the public to keep their distance from the monkeys if they spot one and to dial 911.
The search for the missing monkeys appeared to continue overnight.