At least 23 people were injured, nine critically, after a partial roof collapse and explosion Wednesday in downtown Baltimore, according to the fire department.
The incident occurred at the Baltimore Gas and Electric (BGE) building, according to a tweet from the Baltimore City Fire Department.
Twenty-one people were transported to a hospital and two people declined treatment. Nine people were in critical condition and one person was in serious condition, the fire department said.
The incident is likely construction related and not from natural gas, and occurred while crews were working on the building's air handling and boiler system, a release from BGE said.
A witness told CNN affiliate WJZ the ground shook.
"I was walking on this side of the street past the Radisson (hotel) and the glass on the building shook, and it went boom," Roger Lewis added. "And I didn't know what it was. And we saw debris falling across the street over there."
The building was largely empty because of the upcoming holiday and pandemic, according to the release, and the fire department and BGE crews will continue investigating.
According to the release from BGE, window washing scaffolding was compromised and a window washing crew was pulled to safety by the fire department.
The official cause is unknown at this time, a tweet from the fire department says.