A zoo official in southwestern Poland says seven endangered monkeys have been stolen from their cage for possible sale on the black market.

The Emperor tamarin monkeys, a family of two adults and five of their offspring, were reported missing early Sunday from the Opole Zoo when employees found someone had broken into their enclosure.

The head of the breeding section at the zoo, Krzysztof Kazanowski, said on Monday the monkeys ranged in age from under a year to 10 years old. Mr. Kazanowski said they were probably stolen for someone who wants to own rare and endangered species that are illegal to buy. The tamarin monkey is native to South American rainforests.

The police are investigating the theft.