Posters are being put up around Saint John calling for the return of missing baby monkey, April. (CBC)

Saint John police are continuing to search for a little monkey that was stolen from a local zoo on Tuesday night.

Staff at the Cherry Brook Zoo found a padlock hacksawed and a door kicked in when they arrived at work on Wednesday morning.

A family of Callimico goeldii monkeys were found running free in a hallway, screeching, but one of the small South American marmosets was missing, said Lynda Collrin, spokeswoman with the zoo.

It's an unusual investigation, said Sgt. Pat Bonner.

"We don't know who's really responsible and we'd like to know who they are and what they are and what they want the monkey for," said Bonner. "What the motive would be in taking a monkey is beyond me."

Police have assigned an investigator to take on the case, he said.

The monkey, April, is nine months old and part of an international breeding program of the endangered species.

Collrin said she doesn't know what the monkey would be worth on the black market, but as an endangered animal, it is "priceless" for survival of its species.

"This is a female that could be breeding in the future and producing more animals to make sure these species survive," Collrin said.

Collrin said the zoo isn't interested in pressing charges. They just want April back safely.

Posters are being put up around the port city picturing the brown-eyed monkey, which is about 30 centimetres tall and weighs less than half a kilogram.

A Facebook group has also been set up to help find April.

"There have been no tips so far, but we're not giving up hope," Collrin said.

April's family has been calling for her, Collrin said, and her brother has been searching their enclosure. "It's heartbreaking."

The monkey would not make a good house pet, Collrin said. They require a special diet and can carry disease, she said.

"I just don't want this person to panic," she said. "All we want is for them to return this animal."

With files from the Canadian Press