One of April's family members screeches inside its enclosure at the Cherry Brook Zoo. (CBC)

A stolen young monkey has been returned safely to a New Brunswick zoo.

Saint John police found April, a Callimico goeldii monkey, after they received an anonymous tip from a male caller late Thursday night suggesting they search the Bayside Drive area for the animal that was taken from the Cherry Brook Zoo earlier in the week.

The nine-month-old South American marmoset was found to be missing by the staff at the zoo on Wednesday morning. It appeared a padlock was hacksawed and a door kicked in at the monkey enclosure on Tuesday night. Staff arrived to find the Callimico goeldii monkeys free in a hallway screeching but April was missing.

Police began investigating the theft of the animal while the zoo put up posters around the port city and established a Facebook group calling for her return.

Zoo officials put up posters of April in Saint John calling for her return. (CBC)

Zoo officials told reporters they weren't interested in pressing charges if the monkey, which is an endangered species and part of an international breeding program, was returned safely.

Police found April in a blue plastic box behind a building near a gas station in the Bayside Drive area, said Sgt. Fred Morton.

April was returned to the zoo at about 12:30 a.m. Friday.

"Everybody breathed a sigh of relief," said zoo official Len Collrin. "As soon as we let it out, it chirped and everything seemed all right."

The small animal, which is about 30 centimetres tall and weighs less than half a kilogram, was fed a hearty meal after being returned, Collrin said, and was allowed to rest inside a zoo office for the remainder of the night.

"We're just totally amazed that it is here and very thankful," Collrin said. "Deep in the back of our mind, we kind of wondered if we'd ever see or hear from this monkey again."

Collrin said the zoo had received some reports that April had been spotted in the woods and also suspected she might have been stolen to be sold on the black market.

April was returned to her enclosure to be with her family on Friday morning and was scheduled to be examined by a veterinarian later in the day.

Police are still investigating the case, said Sgt. Pat Bonner. He said police will be focusing on the anonymous telephone call, which came from a payphone, to see if the voice provides any clues to the theft.

The container April was found in is also being examined, Bonner said.

Zoo officials said they are re-examining the security at their facilities.