Multiple monkeys are on the loose in St Louis, Missouri, sparking confusion and concern from the city's animal control officials, who said they do not know where the primates came from.
The monkeys have been running free since at least Thursday, when they were first spotted roaming the streets. Residents have been warned to avoid the exotic animals, as they could be 'unpredictable or aggressive under stress'.
It is unclear how many monkeys are at large, but officials believe there is more than one, and initial reports suggested there were four.
Despite search efforts, the primates had not been found as of Sunday evening, the city's health department, which handles animal control, told BBC News.
A primate expert from St Louis Zoo has identified the animals as vervet monkeys, the health department said.
Vervets are small monkeys, native to Africa, with pale fur and black faces. The health department describes them as 'very intelligent and social' but warns of their potential danger if stressed.
At this time, we do not know where these animals came from, said Justen Hauser, the St Louis health department's bureau chief of environmental health.
Owning exotic animals like primates is prohibited in St Louis, he added, so officials are not aware of any homes where 'illegal monkeys' may have been kept.
Sightings of the monkeys have been reported in the O'Fallon Park neighbourhood in the north of the city, and Hauser believed they were still in this area on Sunday.
Original reports suggested there were four animals, but we cannot confirm an actual number at this time, only that there is more than one, Hauser said.
Marva Young, who lives in the neighbourhood, told local news network KSDK: I think of the danger, because that's a wild animal.
Animal care and control officers have patrolled the area but have not yet managed to locate the monkeys.
We are working to get an idea of where they may be hiding or seeking food, Hauser said.
Residents should report sightings to the health department, as attempts to capture the monkeys should not be made by individuals.
Though owning primates in the city is prohibited, a report noted that Missouri ranks high in primate ownership, with 'at least 35 to 50 primates' bought and sold each year.
The monkeys are not native to the US, but a colony of vervets lives in the wild in Florida, believed to be descendants of escapees from a research centre.
