An explosion in a high-rise building in the US has injured 23 people and temporarily trapped a window cleaning crew on dangling scaffolding.

Twenty-one people were taken to hospital following the explosion in Baltimore, which caused a partial roof collapse.

The city’s fire department tweeted that at least nine of the victims were in critical condition, while another was in serious condition.

The trapped workers were rescued through a window, and firefighters continued to search the building.

The firefighters’ union tweeted that evidence points to an explosion on the 16th floor of the central building, where the offices of Baltimore Gas and Electric Company are located.

The fire department said the cause of the explosion remains under investigation, but utility spokeswoman Stephanie Anne Weaver said work on the building’s “air handling and boiler system” was likely to have caused it.

“Window washing scaffolding was compromised because of the incident and a window washing crew was pulled to safety by the fire department,” Ms Weaver said in a statement.

The building was practically empty because of the holidays and the coronavirus pandemic.