The casualties were German holiday-makers who came to the region on a ski trip. They were believed to have been on their way back from a club when the tragedy occurred. The victims have yet to be identified though reports said all were residents of northern Germany.
The driver, 28, has been detained and was expected to be investigated for homicide. He had a high alcohol blood content when police first arrived.
The largely German-speaking region of northern Italy is a popular tourist destination due to its ski resorts and quaint villages around Bolzano.