Firefighters tackled a large fire at the former Lynton Road neighbourhood housing office in Bermondsey on Saturday afternoon.
The single-storey building, which is next to Fawkham House on the Longfield Estate, has been vacant for several years.
Southwark Council sold the site in 2007 to London & Quadrant Housing Trust for just over £1 million.
Neighbours have previously raised complaints at meetings of Bermondsey Community Council about antisocial behaviour in the empty building.
The site is currently the subject of a planning application for a development of 18 new social rented flats.
Saturday's fire happened just a day after a large blaze on the Sceaux Gardens Estate in Camberwell killed six people.