Two chimpanzees who escaped from their enclosure at Amersfoort’s DierenPark zoo have been shot dead, zoo officials have confirmed.

The two male chimpanzees managed to leave their enclosure at around 10.30, prompting officials to evacuate the zoo. ‘In order to prevent any further escalation, the two male chimpanzees were shot dead,’ the zoo said. ‘We deeply regret this event.’

The zoo says it appears that a keeper did not lock up the enclosure properly, allowing the animals to get out. The investigation will continue in the coming days, but there does not appear to have been a technical error, the statement said.

The decision to shoot the animals, which have been part of the zoo’s chimpanzee group for a long time, was taken because they were demonstrating ‘dominant behavior… which could have led to a dangerous situation,’ the zoo said.

‘This is a black day for the zoo, and we deeply regret the situation,’ the zoo said. Victim support services are being offered to zoo staff and visitors.

A zoo spokeswoman told DutchNews.nl that it would take 10 to 15 minutes for a tranquiliser dart to have an effect on a chimpanzee. ‘ They move very quickly and could have moved inside or outside the park during that time,’ she said. ‘We could have had a disastrous situation, hence the decision not to tranquilise them.