The annual Burning Man festival in Nevada's Black Rock Desert has been marred by a death.

An unidentified woman was killed after falling under a moving bus transporting revellers around the site just after midnight on 27 August (14), according to USA Today.

She was pronounced dead at the scene. It's unclear whether drugs or alcohol played a role in the woman's death.

Burning Man co-founder Marian Goodell says, "This is a terrible accident. Our thoughts and prayers are with her family, friends and campmates. Black Rock Rangers and Emergency Services Department staff are providing support to those affected."

The death is the festival's first such tragedy since a fan fell under a trailer in 2007.

Burning Man 2014 started under a cloud, literally - festivities on Tuesday (26Aug14) were cancelled after rainstorms swept through the site.