All of the missing monkeys in Pennsylvania in the United States have now been accounted for, emergency personnel have said.

Residents of Pennsylvania in the United Sates were warned not to approach the monkeys reported missing in the area following a crash involving a truck that collided with a vehicle which was taking about 100 monkeys to a lab.

The concern from animal welfare experts was that due to the monkeys being in unknown territory and not being domesticated animals, they could not be sure how they might react to a human approaching.

The crash happened on Friday at a state highway exit and it is unclear whether any people or animals were injured as a result.

A widespread search began after small number of monkeys were believed to have fled the crash scene into the surrounding area, but they have all since been located.

The U.S Centers for Disease Control and Prevention provided technical assistance to state police while firefighters used thermal imaging to try to locate the animals, with a helicopter also assisting.