The incident took place in the Baltimore Gas and Electric (BGE) building, according to a tweet from the Baltimore City Fire Department.
Twenty-one people were transported to a regional hospital and two people refused treatment. Nine people were in critical condition and one person was in serious condition, the fire brigade said.
The incident is likely construction-related and not natural gas, and took place while crews were working on the building’s air handling and boiler system, a release from BGE says.
The building was largely vacant due to the upcoming holiday and pandemic, according to the release, and the fire department and BGE crews will continue the investigation.
According to BGE’s release, the window cleaning scaffolding has been compromised and a window cleaning crew has been brought to safety by the fire department.
The official cause is not known at this time, reports a tweet from the fire department.