A pair of male chimpanzees escaped their enclosure at Taipei Zoo on Thursday after keepers failed to properly secure an inner set of doors, forcing staff to tranquilize both animals while visitors were rushed out of the area.

The older of the two, a 44-year-old chimp named Hsiao Chiang, didn't wander far. He stayed near the chimpanzee enclosure and was found visiting with female chimps when veterinary staff hit him with a tranquilizer dart at 5:28 p.m., roughly half an hour after the breakout began.

His younger companion caused more trouble. Wa Chih, an 11-year-old male, took himself on a tour of the zoo grounds, stopping by the giraffe enclosure before scaling a tree near the lion exhibit. When a veterinary team fired the first tranquilizer dart, Wa Chih pulled it out. A second shot, at approximately 5:40 p.m., finally brought him down, UPI reported.

Improperly secured doors gave the chimps their opening

Taipei Zoo's chimpanzee enclosure uses two sets of doors, an inner set and an outer set, as a layered security system. A zoo spokesperson explained that the inner doors had been left improperly secured. The chimps forced those doors open, then pushed through the outer doors to reach public areas of the zoo.

The zoo has not said whether the failure was human error, a mechanical malfunction, or something else. It has not identified who was responsible for securing the doors or how long they had been left in that condition before the animals got out.

The zoo triggered its emergency response plan at approximately 4:55 p.m., when the two chimps left the enclosure. Staff moved quickly to usher visitors out of the surrounding area and set up barricades to contain the animals while veterinary teams moved in with tranquilizers.

Both chimps recovered by evening, but questions remain

After the tranquilizers took effect, a veterinarian examined both animals. Neither chimp was harmed. Staff moved them to an indoor enclosure, and both woke up at approximately 8:00 p.m.

The zoo issued a news release confirming the incident and stated that procedures are under review to prevent a repeat. But the statement left key questions unanswered: whether any visitors or staff were injured during the episode, what specific protocols failed, and what corrective steps the zoo plans to take.

No reports of injuries to visitors or staff appeared in the zoo's account of the incident.

When a zoo can't keep its enclosure doors locked, the review it promises afterward is the least the public should expect, not the most.