The woman, thought to be 18 years old, fell to her death as police raided an address in Woolwich, south-east London.
The Independent Police Complaints Commission (IPCC) has been informed of the death. The Metropolitan police service directorate of professional standards is also investigating the incident.
A Scotland Yard spokesman said: “Shortly after the officers entered the flat, a woman – who is believed to be 18 – fell from a bedroom window on the 17th floor.
“She was pronounced dead at the scene.”
He added that a man had been arrested “on suspicion of assisting an offender”, and is in custody at a south London police station.
A formal identification of the body is yet to be made.