BOZEMAN, Mont. (Associated Press) -- A man who drove a bus full of Bozeman middle school students into Yellowstone National Park after a night of drinking has pleaded guilty in federal court in Mammoth Hot Springs, Wyo.

The Bozeman Daily Chronicle reports 42-year-old Kevin Leon Stark pleaded guilty Thursday to operating a commercial vehicle with "a detectable amount of alcohol."

Federal prosecutors say Stark's blood-alcohol level was 0.032, below the limit of 0.04 at which a commercial driver can be charged with driving under the influence.

Prosecutors will recommend Star be sentenced to 30 days in jail and fined $750.

Stark and Jack Parrent, both of Bozeman, were arrested June 3.

Court records say Parrent's blood-alcohol content was 0.12. His trial is set for next week.