The scary accident happened Saturday night at the Las Vegas festival ... a huge camera fell about 35 feet, landing on top of the victims. We're told the camera was fastened to a cable, but slipped off ... sending the camera and pieces of its rigging plummeting into the crowd.

We're told the whole apparatus weighs about 20 pounds!

All 3 women were treated on scene, but 2 of them needed more assistance and had to be rushed to a hospital. We're told one woman was treated for a head injury, and the other for a leg injury. They've both been released.

The group Of Monsters and Men was performing on the main stage when the camera free fell ... creating, as you can see, a very bloody scene.

A rep for the festival tells us, "The safety and security of our guests, partners, artists and employees is our first priority. Our thoughts and well wishes are with those affected by the incident." They also say there is an ongoing investigation and they are working to identify the cause of the incident.

It's the second straight year equipment has injured people at Life is Beautiful.