Okotoks RCMP are investigating after a single-vehicle crash left one person dead and sent four others to hospital in serious condition.

Police were on scene at the crash, which took place at 112 Street W. in Okotoks, Alta., approximately one kilometre north of Highway 549, at around 9 p.m. MDT on Saturday evening.

Police said in a release that a collision analyst will be investigating.

RCMP are rerouting traffic from the area so police can safely investigate.

There were a number of multi-vehicle collisions around Calgary and on southern Alberta highways on Saturday.

A snowfall warning for much of southwestern Alberta was in effect on Saturday evening.

The warning, issued by Environment Canada, warned of heavy snowfall of 15 to 25 centimetres, with another 10 to 15 centimetres expected overnight, for Cardston, Crowsnest Pass, Kananaskis, Lethbridge and Okotoks.