So many people have climbed Mount Everest these days that it’s sometimes easy to forget that scaling the world’s highest peak is a massively dangerous undertaking.

This morning we woke up to news that hammered the point home in the most brutal fashion. At least 13 local climbers have been killed by a massive avalanche, which swept them away as they were preparing routes for the tourists who will arrive to attempt the climb during the main summer season.

Video footage taken from the 2006 documentary Everest: Beyond the Limit, which shows an avalanche hitting the Khumbu ice-fall, the same area where the climbers were killed yesterday.

The death toll makes this one of the deadliest single incidents ever on the slopes of the 8,848m mountain, and it may yet rise.

According to newspaper reports the 13 were part of a party of 25 sherpas, not all of whom are yet accounted for. Three injured climbers were taken to hospital in Kathmandu, but as many as seven may still be missing.

“The death toll makes this one of the deadliest single incidents ever on the slopes of the 8,848m mountain, and it may yet rise.”

The group were fixing ropes and scoping a new route through the treacherous “ice-fall” section between base camp and camp one on the ‘classic’ South Col route. This steep, frozen glacier shifts slightly every season, so a new route has to be found through the treacherous crevasses every year.

Mohan Krishna Sapkota, an official from the tourism ministry confirmed: “The sherpa guides were carrying up equipment and other necessities for climbers, when the disaster happened.”

With May being the optimum time to try and scale the peak, the sherpas were preparing the way for the annual influx of eager climbers.

This tragic incident is sure to re-ignite the long-running debates about the ethics and economics of mass tourism in one of the world’s most dangerous places.