A toy ape is placed between candles at the entrance of the zoo in Krefeld, Germany. Picture: Alexander Forstreuter/dpa via AP

Krefeld, Germany - The zoo in the western German city of Krefeld reopened on Friday, two days after a fire destroyed its renowned Great Ape House, killing 30 animals.

Visitors began queueing ahead of the opening at 9 am (0800 GMT). Others lit candles to mark their sorrow over the loss of monkeys and other primates, including chimpanzees, five orangutans and two elderly gorillas.

The Great Ape House caught fire shortly after midnight on Wednesday, apparently after a Chinese lantern had landed on it.

A 60-year-old woman and her two grown-up daughters turned themselves into police in the belief that they had inadvertently caused the fire. They said they had lit five Chinese lanterns, one of which "with a probability bordering on certainty," according to police, had set fire to the ape enclosure.

An exterior view of the destroyed ape house of the zoo in Krefeld, Germany. Three women are under investigation for launching paper sky lanterns blamed for setting off a fire that destroyed an ape house at the zoo, killing more than 30 animals. Picture: Marcel Kusch/dpa via AP

The women are now being investigated for negligent arson and could face up to five years in prison or a fine if they are found guilty.

People mourn outside the zoo in Krefeld after a monkey house burned down. Picture: Thilo Schmuelgen/Reuters
Firefighters hold candles outside the zoo in Krefeld after a monkey house burned down. Picture: Thilo Schmuelgen/Reuters
A toy monkey is seen between flowers and candles outside the zoo of Krefeld. Picture: Thilo Schmuelgen/Reuters
People mourn outside the zoo in Krefeld after a monkey house burned down. Picture: Thilo Schmuelgen/Reuters

They said they had ordered the Chinese lanterns online, without realizing that they were illegal across most of Germany.

Krefeld Zoo said it had received thousands of donations, as well as offers of assistance from other German zoos.

dpa