A hotel in a historic downtown Atlanta building was evacuated Friday morning and will remain closed until at least Tuesday after several guests were taken to local hospitals to be monitored for possible carbon monoxide poisoning.

Firefighters were called to the Residence Inn by Marriott at 134 Peachtree Street just after 9 a.m., officials confirmed. Atlanta Fire Rescue Assistant Chief Greg Gray said five people, three adults and two children, were taken to Grady Memorial Hospital and Hughes Spalding Hospital.

A spokeswoman for Grady said she could not provide any patient information, citing privacy concerns. Children’s Healthcare of Atlanta, which runs Hughes Spalding, did not immediately respond to an inquiry about the patients’ status.

Carbon monoxide, a colorless, odorless gas, is the second-most common cause of non-medical poisoning, according to the Centers for Disease Control and Prevention. It is a byproduct of combustion and can be found in fumes produced by running cars, furnaces and other gas-powered appliances. Common signs of carbon monoxide poisoning include headache, dizziness, weakness, upset stomach, vomiting, chest pain and disorientation, but exposure to large concentrations can cause sudden death.

Gray said the fire department received a call from the hotel at around 8:30 a.m. reporting that guests were feeling ill. A single fire engine was initially dispatched, but once responders arrived, Gray said it became apparent there was a carbon monoxide “issue throughout the building.”

About 80 fire rescue staff were ultimately deployed to the scene and responders made the decision to evacuate the entire 20-floor hotel, he said.

Residence Inn staff said 100 of the hotel’s 160 rooms were occupied at the time, Gray said. To speed up the process, firefighters pulled the fire alarm, and Gray said it took about an hour to get all guests out of the building.

Firefighters spent Friday morning monitoring carbon monoxide levels and using large floor fans to ventilate the hotel.

At around 12:30 p.m., the last of the fire engines that responded to the situation pulled away, but a hotel staffer said the building would remain closed at least until Tuesday. The staffer said the cause was a carbon monoxide leak, but would not elaborate.

Some guests who were forced to evacuate reported feeling sick Friday morning and said they were left shaken by the incident.

Dave Adams stayed on the hotel’s 19th floor Thursday night with his wife and children. At around 8 a.m., his two daughters said they had headaches and weren’t feeling well, but he thought it might be dehydration-related.

Adams said they went downstairs to have breakfast but were forced to leave when the fire alarm went off. He said his daughters’ symptoms had subsided, but that the ordeal was scary.

“We didn’t know what was going on at first, so it was pretty upsetting,” he said.

On Friday afternoon, hotel guests said the Residence Inn was working to book rooms for them at other hotels in the area.

Marriott International, which owns the Residence Inn, did not immediately respond to a request for comment.

The hotel is located in the Rhodes-Haverty building, which was Atlanta’s tallest building when it was constructed in 1929, according to the National Register of Historic Places.

Georgia law requires all new homes with a gas appliance or attached garage to have a carbon monoxide detector installed but does not require carbon monoxide detectors in temporary lodging like hotels.