The Canadian pop singer Justin Bieber will have to pay thousands of euros to an animal shelter caring for the pet monkey seized two months ago by German customs officials.

The customs office in Munich said Bieber has until midnight on Friday to contact them, otherwise Mally, the singer's capuchin monkey, would become "property of the state" and would be transferred to a permanent home at a zoo or animal park elsewhere in Germany.

Mally was seized by German customs on 28 March when Bieber, 19, failed to produce required vaccination and import papers after landing in Munich while on tour. It was quarantined and cared for at the city's animal shelter, where the manager, Karl Heinz Joachim, said Mally, now 20 weeks old, had fared well and gained weight.

The shelter has criticised Bieber for keeping such a young monkey as a pet, saying the animal should not have been taken away from its mother until it was a year old. Experts say capuchin monkeys also need to be kept in groups as they are very sociable animals.

"The best thing would be not to buy one at all, but if you do, buy five," said Joachim.

He said emails from Bieber's management to the shelter indicated the singer does not want the monkey anymore, but that the final decision would have to be made by German authorities.

"Our contact is the person that the monkey belongs to," said Munich customs spokesman Thomas Meister. "We've had contact with lots of people but none of them was an authorised representative."

Meister said the cost of care, food and vet visits at the Munich shelter amounted to several thousand euros.

"You can bet we are going to ask for that money back," he said.