The six-story Capita Group building was evacuated after the explosion at 9:40 a.m., the BBC reported.
Ambulance officials said the woman's injuries were relatively minor, affecting her hands, the This Is Local London Web site reported.
Chief Superintendent Ian Thomas refused to comment on who might be responsible for the explosion, which happened just 200 yards from Scotland Yard's headquarters, the BBC said.
The Capita Group is a major British business process outsourcing and professional services company, with clients including the city of London and the BBC.
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