A fire overnight destroyed Krefeld Zoo's Great Ape House, killing most of the primates inside, the zoo said in a statement on Facebook.

More than 30 animals were killed, including orang-utans, chimpanzees, gorillas and marmosets. A nearby gorilla garden was undamaged.

Read more: Ape hit: German zoo animals go wild for gifts

Police said that, after a press conference appealing for information, several people had made statements to them about how the fire might have started.

Officials have yet to confirm whether or not any individual is to be charged.

Firefighters spent hours fighting the fire

'Still in shock'

The zoo said it was thankful for "numerous offers of help" but that it wasn't clear yet where assistance was most needed.

"We are still in shock and cannot yet say exactly if and where help is needed," it said in a statement.

Read more: Germany sees spike in experiments on monkeys

The ape house was built in 1975 and was home to several primate species.

No animals survived the fire, according to the zoo

Searching for the cause

Police said an initial investigation had determined sky lanterns had set light to the plastic roof of the monkey-house and caused the rest of the structure to go up in flames.

The Chinese miniature hot air balloons have been banned in the state of North Rhine-Westphalia since 2009 after several fires started by them caused deaths.

Germany is the largest importer of fireworks in the EU. Each year on New Year's Eve, hundreds of thousands of firework enthusiasts set off light explosives across the country.

Read more: Germany slammed over rise in animal testing

How alike are apes and humans? The human ape Apes are beloved in the arts - especially when it comes to philosophizing over the human condition. Primates were turned into literary monuments by writers such as E.T.A. Hoffmann, Wilhelm Hauff and Franz Kafka. Koko, the talking gorilla lady, became famous in the 1970s. A documentary by Barbet Schroeder (1978) shows the animal's training - or brainwashing.

How alike are apes and humans? Beauty and the beast The Berlin museum Haus der Kulturen der Welt is now reviewing primates in the arts. Here, a diplomat's wife takes chimpanzee Max as a lover. In the comedy "Max, Mon Amour" (1986), Japanese director Nagisa Oshima pokes fun at the social changes in the status of women. Billed as "the greatest ape romance since King Kong," the film satirizes extramarital affairs among the Parisian upper class.

How alike are apes and humans? The thinker? Natural sciences and popular culture illustrate how our perception of monkeys has radically changed over time. The artist Klaus Weber made a critical study of the image of great apes. His photo collage "Beulen" (2008) shows a plastic primate in a thinker pose, surrounded by heads of famous people popping up around him like comic bubbles.

How alike are apes and humans? Reinterpreting reality For his project "Flota Nfumu" (2009), Filip Van Dingenen was inspired by the Spanish albino gorilla Snowflake, who was the most famous resident of the Barcelona zoo from 1966 to 2003. His human-like facial expressions made him a pop culture star. In his large installation, Van Dingenen collected children's pictures to show the cult surrounding "Nfumu," as the gorilla was originally called.

How alike are apes and humans? Monkeys and power The ape-faced god Hanuman is an important figure in Javanese culture. In street theater plays, he will typically behave like a lord and master who teaches societal norms to the audience. The at times surrealist film "The Masked Monkeys" (2014), by Anja Dornieden and Juan David Gonzales Monroy, questions the working conditions and power relationships between Javanese monkeys and their owners.

How alike are apes and humans? Human mask The French artist Pierre Huyghe was inspired by a YouTube video for his short film. The clip "Fuku-chan monkey in wig, mask, works restaurant" features a monkey in a restaurant in Tokyo who wears a mask and a wig, which make him look like a small girl. Huyghe found that monkey to create his own 19-minute film, "Human Mask," where the animal poetically moves like a Japanese Noh performer.

How alike are apes and humans? Visions of a chimpanzee The "Planet of the Apes" movies which started being released in 1968 created new fantasy worlds, and their imagery is now an integral part of pop culture, especially in the US. Coco Fusco's video "TED Ethology: Primate Visions of the Human Mind" (2015) offers a lecture by Dr. Zira, who was the feminist chimpanzee researcher in the cult movie series.

How alike are apes and humans? The ape in me Erik Steinbrecher works with multi-layered images and puns. His installation "AFFE" (APE, 2015), made of various natural and inorganic materials, leaves room for interpretation. The exhibition "Ape Culture" at the Haus der Kulturen der Welt in Berlin runs through July 6, 2015. Author: Sabine Peschel / eg



cw,ls,rc/mm (dpa, AFP)

Every evening, DW's editors send out a selection of the day's hard news and quality feature journalism. You can sign up to receive it directly here.