Fatal snowmobile crashes increased nearly 50 percent in Michigan last winter with two out of every three involving alcohol.

According to a summary by the Department of Natural ResourcesÂ’ Law Division released last month, there were 23 fatal accidents during the 2012-13 season, 15 involved the use of drugs or alcohol.

That compares with 16 fatal accidents in 2012, with seven of those involving intoxicants.

DNR officials say most snowmobile accidents are caused by excessive speed, operator fatigue, or the use of alcohol and often itÂ’s a combination of several of those factors.

The stateÂ’s lowest number of snowmobile fatalities in 20 years occured in 2011 with 13 deaths, five of those involved alcohol.

The highest death toll in the last nine years occurred during the 2009-10 season when 26 people died in snowmobile crashes.