Naperville, IL – A hotel on Naperville’s far north side was evacuated Monday morning due to high levels of carbon monoxide and natural gas.

Emergency personnel responded to Hotel Arista, 2139 City Gate Lane, about 4:27 a.m., according to fire officials. They performed a room-to-room search to make sure all occupants of the 12-story building had been evacuated.

Guests were relocated to a nearby building and none reported illness, fire officials said in a news release.

Firefighters working with Nicor determined the elevated natural gas and carbon monoxide levels were caused by a malfunctioning heating, ventilation and air conditioning unit on the roof of the building. The building was ventilated to bring the readings of the gas to zero before occupants were allowed to return.