Boys aged five and seven sleeping in friend's apartment above shop in Canada when snake escaped through ventilation system

A python escaped from its enclosure at a pet store in Canada, worked its way through a ventilation system into an upstairs apartment and killed two young boys as they slept, police have said.

The brothers, aged five and seven, were visiting the apartment of a friend above Reptile Ocean, an exotic pet store in Campbellton, New Brunswick, said Royal Canadian Mounted Police Constable Julie Rogers-Marsh.

Police arrived at the apartment around 6.30am and found the two boys dead. A friend of the boys was sleeping in another room and was unharmed, Rogers-Marsh said. She said the owner of the pet store lived in the apartment.

Rogers-Marsh said the snake escaped from its enclosure sometime during the night and was believed to have made its way into the apartment through the ventilation system. "It's believed the two boys were strangled by the snake," she said.

The snake was captured and was in the possession of police, Rogers-Marsh said. Calls to the pet store were not returned on Monday.

Rogers-Marsh said autopsies were to be performed on the two victims on Tuesday.

"It's very, very unusual and very tragic and difficult for everyone involved," Rogers-Marsh said.

The town's deputy mayor, Ian Comeau, said Reptile Ocean was licensed to operate and "everything was according to our bylaws, to the provincial guidelines".

The deaths of the boys have been "a shock ... it is unbelievable", Comeau said Monday evening. Comeau said he saw alligators, crocodiles and snakes when he toured the shop with the fire department about two years ago.