(CNN) Dozens of animals were killed when a fire tore through a monkey enclosure at Krefeld Zoo in northwestern Germany in the early hours of New Year's Day.

"Our Monkey House fell victim to a fire that started more or less around midnight," zoo director Wolfgang Dressen told reporters at a media conference. "We don't know exactly when it started yet, but it burned down the house completely."

Dressen said at least 30 animals died and that it was "the hardest day that Krefeld Zoo has ever had," according to CNN affiliate ARD.

"For us it is especially tragic that the tenants of this house, birds and mammals, were victims of the fire last night," he added. "Among them were highly endangered monkeys like orangutans from Borneo, lowland gorillas from Central Africa and chimpanzees from West Africa."

Firefighters examine the enclosure at Krefeld Zoo, following a blaze that left scores of animals dead.

In a statement on its Facebook page, the zoo said two chimpanzees -- named Bally and Limbo -- survived the blaze, "like a miracle ... they are only slightly injured." It said the pair are being taken care of by veterinarians.

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