The town of Churchill in Canada’s far north will expand its unique "polar bear jail" to house more wayward carnivores and reduce the threat of bear attacks, an official said.

The facility, built in 1980 in the world’s polar bear capital, will also be cooled now over the summer to make the furry inmates’ incarceration "a bit more bearable," said Shaun Bobier of the Manitoba Conservation Department.

Polar bears that wander into town in summer or autumn are now captured if they cannot be easily scared off. They are held in one of 23 cells divided by cinder block walls until ice forms on nearby Hudson’s Bay and then released, Bobier said.

However, if the facility becomes overcrowded, some bears are relocated far away by helicopter.

With five new cells to be added soon, conservation officers will be able to hold more bears for longer periods, and then drive them out onto the ice floes when winter comes, Bobier said.

Last year, 58 bears were housed in the triple Quonset jail. In 2004, 170 bears were kept behind bars, fed only water and ice to ensure "they don’t start coming to here for the food," Bobier said.

The meagre prison grub is not cruel or unusual, he noted. The bears typically feast on seals in winter and fast in summer.

The last fatal bear attack in Churchill was in 1983, three years after the jail was built. But, there have been several human-bear skirmishes since, he said.