Two Royal Bengal Tigers sneaked out of an off-exhibit enclosure in the Assam State Zoo here around 10.30 a.m. on Saturday. They roamed in the open, triggering panic among visitors for nearly three hours. They were subsequently tranquillised by the zoo veterinarian and put back in their enclosures.

Tigress Divya and her cub, born in the zoo on May 8, 2008, escaped from the enclosure through a door which was kept open by the animal keepers while disinfecting it.

Terming the incident “unfortunate,” Divisional Forest Officer Narayan Mahantasaid the door was kept open due to lack of coordination among the three animal keepers who were cleaning the enclosure.

“We will carry out an investigation to find out how it happened and take all measures to ensure that such incidents do not recur,” he added.

On December 19, 2007, Divya and her male partner mauled a visitor to death. His wife, sons and dozens of horrified visitors watched helplessly as the victim tried to free himself from the biting grip of the big cats. He later died of injuries. Divya was born in the Shimoga zoo-cum-safari, Mysore, on February 19, 2002, and brought here on February 19, 2005.

Seeing the two big cats walking lazily in the open, horrified visitors ran helter-skelter. Zoo officials and staff, led by Mr. Mahanta swung into action and evacuated visitors quickly. Then, they started trailing the tigers in the undulating areas of the zoo.

They also alerted residents of adjacent localities as there was a possibility of the tigers crossing the boundary wall. Police officials also rushed to the zoo to assist the authorities.

The cub was tranquillised with a single shot from the dart gun, while Divya continued to roam about even after the first shot and had to be given a second.

The zoo was reopened to visitors after the nearly three-hour-long drama. It being a government holiday, there was a rush of visitors since morning.

This is the first incident of big cats escaping from their enclosure. In December 2009, a visitor’s wallet fell inside an enclosure.