Two teenage boys are dead and six others are injured after a late-night tobogganing excursion on the Olympic bobsleigh track in Calgary.

Calgary's Police Service has not determined how the boys accessed the twisty racing facility. Security at Canada Olympic Park, known as COP, called emergency crews around 1:30 a.m. Saturday. They found eight young men in various states of injury.

"Part way down, the group hit a large gate used to separate the bobsled and luge tracks," CPS said in a statement. The group was riding a "personal sled/toboggan."

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Two boys were declared dead at the scene, and six survivors were taken to hospital. One of the survivors is in "critical" condition and the other five are being "treated for their injuries," CPS Duty Staff Sgt. Paul Wyatt told reporters Saturday morning.

Investigators believe are the victims are in their "late teens." Police are having difficulty identifying the boys because of the extent of their injuries. The six survivors are "severely traumatized,"‎ Sgt. Wyatt said. "So we're having a hard time... getting information from them at the hospital."

Police have information related to the owners of two vehicles believed to be involved in the incident. Sgt. Wyatt, however, would not confirm whether CPS has determined if they were involved. "We're still notifying next of kin," he said when asked about confirmation.

Three of the injured boys were transported to the nearby Foothills Medical Centre with "multiple, quite serious, soft tissue-type injuries," Emergency Medical Services spokesman Adam Loria told reporters. They are considered "stable and non-life-threatening." The remaining trio were taken to the Rockyview General Hospital with "minor injuries and stable condition," he said. ‎

The sliding track, which was used in the 1988 Olympic Games, is on the World Cup circuit. Athletes also use it for training. The track was closed at the time, but the top of the Olympic facility can be easily accessed. It is just on the other side of a fence separating it from suburban homes. Intruders could also climb the short chain-link fence surrounding the top of the park, which is across a street from the residential area. Further, the track is part of the larger COP complex and could be accessed from the base of the hill.

The weather was favourable when emergency responders arrived, Mr. Loria said, but given the location of the incident, some of the area where they had to work was "quite slippery."

Police have brought in the CPS Traffic Reconstruction Unit as well as officers from the Centralized General Investigations Section. WinSport Canada, which runs COP, is co-operating with police and providing security camera footage. ‎CPS is also gathering security footage from nearby residents.

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"On behalf of WinSport, I would like to express our sincerest sympathies to the families of the two deceased," Barry Heck, Winsport's president, said in a statement. "Our thoughts and prayers are with their families."

On Saturday, COP lowered the giant Canadian flag at the top of the ski hill to half-mast.

The bobsleigh track is open to the public in the summer, but visitors are accompanied by a "professional pilot," according to WinSport. The ride covers 10 turns, including the "famous Omega and Kreisel" corners. Guests can reach speed of up to 80 kilometres per hour, WinSport says.

WinSport has also transformed the Olympic ski jump facility into a zipline ride in the summer.