Waterloo fire officials say an investigator determined three juveniles intentionally set a fire in a hallway inside a three-story apartment building. Emergency crews were called to the 1300 block of West Donald Street on Sunday around 9 a.m. Battalion Chief Ben Peterson said the fire was put out before they arrived. Firefighters ventilated the building and then called the investigator. There were no injuries and damage was minimal, according to Peterson. Waterloo police said they're also investigating the fire. There have been no charges filed at this time.