Two men were charged Monday with stealing rare pygmy marmosets from an Australian wildlife park as a baby was reunited with her mum and the hunt continued to find dad.

Three of the monkeys, the world's smallest, were snatched from their enclosure at the Symbio Wildlife Park south of Sydney on Saturday, with police and zookeepers launching a desperate bid to locate the suckling infant. 

There were fears it would die if away from its mother for more than 24 hours while keepers also worried its twin would perish because their mother was too stressed to feed.

After a tip-off from the public, two men, aged 23 and 26, were arrested and charged Monday with dealing with the proceeds of crime.

Police found the unnamed four-week-old infant in the men's car and a 10-month-old female, Sophia, at another address. But the father, Gomez, remains missing.

It was not clear why the monkeys, which are native to South America and usually about 20 centimetres (eight inches) tall, were taken, but Symbio park manager Matthew Radnidge said there would have been a financial motivation.

"But in terms of value, an animal has a value of whatever someone perceives, so within the zoo and wildlife park industry, no money ever changes hands with these animal transfers," he told ABC radio.

Sydney's Daily Telegraph said marmosets, also known as thumb monkeys, were in demand on the black market as pets, commanding prices of up to Aus$5,000 (US$3,700).

The wildlife park said the hungry and scared baby had been reunited with its mother and sister.

"Mum cradled the baby straight into her arms and bub immediately began to feed," the park said on its Facebook page.

"Early observations this morning are promising, with two bright eyed twins observed on mum's back -- so a great result."