DULUTH, MN (KDAL) - About 30 people were evacuated from Fryberger Arena in Duluth last night when dangerously high levels of carbon monoxide were detected.  Firefighters called for an ambulance after 8 people with elevated blood levels of carbon monoxide complained of headaches and nausea. Only one person was taken from the scene to the emergency room for treatment.  Hockey teams that had played earlier in the evening were notified and another person was transported to the emergency room from home.  The cause of the high levels of carbon monoxide in the building is under investigation but suspected causes include a propane powered Zamboni and aging heating and water heating systems.