Last I heard were six fatalities. Since it is breaking news, those numbers are subject to change. I've heard most of the occupants were Korean. I've heard some children were on the bus. Some reports said the accident was 27 miles south of Hoover Dam on Highway 93.
I saw some pictures. It is a smaller bus, much like the shuttle busses most car rental places (except Vegas) use. The bus was on it's side.
Many of the injured are being flown by helicopter to Las Vegas since there are no major hospitals nearby.