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Police are on the hunt for 43 monkeys who escaped from a research facility in South Carolina, after a keeper left their pen open.

The rhesus macaque fugitives broke out of Alpha Genesis, a company that breeds primates for medical testing and research, and are on the loose in a part of the state known as the Lowcountry.

Authorities have urged residents to keep their doors and windows securely closed and to report any sightings immediately. The escaped monkeys are young females, weighing about 7lbs (3.2kg) each, according to the Yemassee Police Department.

Police said on Thursday that the company had located the "skittish" group, and "are working to entice them with food".

"Please do not attempt to approach these animals under any circumstances," police said.

The statement added that traps had been set in the area, and police were on-site "utilizing thermal-imaging cameras in an attempt to locate the animals".

Police say the research company has told them that because of their size, the monkeys have not yet been tested on and "are too young to carry disease".

Greg Westergaard, CEO of Alpha Genesis, called the escape "frustrating".

He told CBS News, the ´óÏó´«Ã½'s US partner network, that he was "hoping for a happy ending", and that the monkeys would return to the facility on their own.

Mr Westergaard said the monkeys had escaped on Wednesday after a keeper left a door open to their outdoor enclosure. He said they were now "hanging out in the woods".

"It's really like follow-the-leader. You see one go and the others go," Mr Westergaard said.

"It was a group of 50, and 7 stayed behind and 43 bolted out the door."

"There are some little things to eat in the woods but no apples which are what they really like, " he said, "so we are hoping that will draw them in the next day or two".

Speaking to South Carolina newspaper , he added that capturing the monkeys had been made more difficult due to the weather, saying efforts were "hampered a bit by the rain as the monkeys are hunkered down".

According to The Post and Courier, this is not the first time that monkeys have escaped from the facility.

In 2016, 19 monkeys escaped before being returned about six hours later. Two years earlier, 26 primates escaped the facility.

The town of Yemassee, 60 miles (100km) east of Charleston, has a population of fewer than 1,100 residents.

Congresswoman Nancy Mace, who represents South Carolina in the House of Representatives, tweeted that her office is "diligently gathering all relevant information to keep our constituents informed regarding the recent escape of primates".

Macaques are known for being aggressive and competitive. However, Yemassee Police Chief Gregory Alexander said, in a news conference on Thursday, that "there is almost no danger to the public".

Earlier this year, a Japanese macaque named Honshu escaped from a zoo in Scotland.

After more than five days on the loose, he was located by a drone and then shot with a tranquiliser dart before being returned to the zoo.