In another hour, Ty Stiffarm could have frozen to death. That's what his mother, Brooklynn Wait, said she was told by doctors after she brought her 3-year-old son into the hospital in Cloquet on Monday after he was found alone and screaming on a Fond du Lac Head Start bus.

Ty was strapped into his seat behind the driver, Wait said, and "there is no excuse" for him to be forgotten on the bus. It is estimated he was alone on the bus for at least three hours. Ty's mother said he usually gets to Head Start just after 7 a.m. Someone passing by the bus at 11 a.m. heard screaming and called for help, Wait said.

"He said, 'I was crying and nobody helped me,' " she said.

He was warmed up at the hospital and was released in about three hours, his mother said Monday night. He was a bit more lethargic than his usual self, she said, and his hands and feet were still purple nearly eight hours after he was found.

The Fond Du Lac Band of Lake Superior Chippewa is investigating why Ty was left on the bus in temperatures hovering at 0 degrees.

According to the band, the driver of the bus did not check to see whether all students had left the bus after it stopped at the Head Start on tribal land near Cloquet. Tribal attorney Dennis Peterson said, "we're looking into it."

Fond du Lac runs its own transportation system and drivers are trained to search their buses after dropping students off, Peterson said.

Tribal chairwoman Karen Diver said the employees involved have been placed on administrative leave while an investigation continues.

"Tribal administration is taking it very seriously but do not have all the facts yet," she said.

Wait said she's concerned about staff at the Head Start not taking attendance right away at the school. If they had, they could have called her and known much earlier that Ty was missing, she said. She said school officials told her they would begin taking attendance earlier in the day.

Ty was found at 11 a.m. but his mother wasn't called until 11:30 a.m., Wait said. She said staff volunteered to take him to the hospital but she told them she would. She said she was puzzled why staff didn't immediately call her and seek medical attention. She told them so.

"They understood they should have called an ambulance," Wait said.

"He's usually rambunctious," she said of reuniting with her son at Head Start. "When I got there he was distraught, just sitting there."

She said that later in the day the bus driver came by her home to offer an apology. She said that doesn't help explain how her son was left on the bus.

"They could not give me that info," she said.

Wait said she will meet today with tribal officials and the Head Start director to get a full report on what happened.

Joe Cadotte contributed to this report.